Download AS/400 Java

Database Access
▮ JDBC
▮ DB Access objects
▮ Encapsulation
▮ Abstract classes
▮ CRUD
chapter 10
© copyright Janson Industries 2011
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Database Access
▮ Need DBMS-specific software (called a
driver) to access the various DBMSs
▮ Why? Java follows a DB access protocol
called JDBC (Java DB Connectivity)
▮ None of the DBMSs directly support JDBC
▮ However each DBMS vendor supplies a driver
▮ The driver converts JDBC requests to the
DBMS’s protocol
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Drivers
DBMS
Drivers
DB2
Oracle
ODBC
chapter 10
Java Pgm
JDBC
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Drivers
▮ ODBC (Open DB Connectivity) is the MS
Access DBMS’s protocol
▮ sun.jdbc.odbc.JdbcOdbcDriver, the driver
class, is included in the JRE (and RAD)
▮ For DB2 and Oracle you must download
the driver and include in classpath
▮ The headache with Access is you must
define the DB as an ODBC data source
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Drivers
▮ For Access: DB must reside and be defined
as an ODBC data source on the computer
where the application will run
▮ To run in RAD or as an application this means
on the client
▮ To run on a server, this means on the
computer that is acting as the server
▮ An Access DB cannot be accessed remotely
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Drivers
▮ For other DBMS’s:
▮ Download the driver
▮ Set the class path to point to the driver
▮ To run in RAD: change the Java Build Path
▮ To run on a client or server: change that
computer’s classpath environment variable to
point to the driver
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Running on client
▮ For instance to access DB2 on a IBM
Power System:
ADDENVVAR ENVVAR(CLASSPATH)
VALUE('/QIBM/ProdData/Http/Public/jt400/lib/jt400.zip')
▮ On a Windows PC, change the set
classpath to include jt400.zip
path=c:\jdk\bin
Set classpath=.;\jdk\lib\tools.jar;c:\jtopen\lib\jt400.jar
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Accessing a DB
▮ In a java pgm, 4 things, several steps:
▮ 1. Register/load the driver
▮ 2. Get a Connection object, using the
DriverManager class
▮ 3. Create a Statement object, using the
Connection object
▮ 4. Define and execute SQL statements,
using the Statement object
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Accessing a DB
▮ The Class class (yikes!) allows you to
register/load the driver
▮ A DriverManager allows you to get a
Connection object
▮ A Connection allows you to create a
Statement object
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Register/load the driver
▮ Instead of “instantiating an object of the
driver”, load (register) the driver in the
JVM with the “class loader”:
Class.forName(“com.ibm.db2.jdbc.app.DB2Driver”)
▮ Essentially returns a driver object (of the
type specified) as a Class object and
makes it available to the JVM
▮ Just like getInstance(), another way to
create an object
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Connection Object
▮ A DBMS connection must be established
(even if the Java application is running on
the same machine as the DBMS)
▮ To create a Connection must specify the
▮ Driver to be used
▮ DB (possibly including a URL or IP address)
▮ Optionally, a user ID and PW
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DB Identifier
▮ Identified as: driver:subprotocol:subname
static String url = ("jdbc:db2:subprotocol:subname);
▮ Optional subprotocol ids a DB connectivity
mechanism (supported by the driver)
▮ The subname ids the DB and its syntax
depends on the protocol and subprotocol
▮ If specifying a network address as the
subname, follow the standard naming
convention of: //hostname:port/subsubname
▮ Subsubname has unique internal syntax
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DB URL
▮ For MS Access on Windows
static String url = ("jdbc:odbc:TNT Database”);
▮ For Oracle
static String url=("jdbc:oracle:thin:@1.2.3.4:1521:SID”);
▮ For DB2 on an IBM Power System
static String url = ("jdbc:as400:1.2.3.4”);
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Properties Object
▮ Properties hold information for the driver
▮ Each driver expects its own set of info
▮ Most drivers expect user ID and password
(not MS Access)
▮ You can create a property object and then
set the values
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static Properties p = new Properties();
:
:
:
File naming
p.put("naming", "sql");
p.put("user", "rjanson");
convention
p.put("password",
“jeter");
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Get a Connection Object
▮ Create a Connection object with the
DriverManager’s static getConnection
method
▮ Pass the String url and Properties object
con = DriverManager.getConnection(url, p);
▮ DriverManager searches for a suitable
driver from those that were loaded (e.g.,
those that were registered with the
.forName method) based on the protocol
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Statement Object
▮ Created with the Connection object’s
createStatement method
Statement stmt = con.createStatement();
▮ Primary methods to perform SQL
instructions:
▮ executeQuery – SQL Select command
▮ executeUpdate – SQL Insert, Delete, Update
stmt.executeUpdate("INSERT INTO TNTDB.CUSTOMER " +
"VALUES(1, 'Joe Customer', '1 Main St.', " +
"'Jacksonville, FL 32233')");
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Java Changes
▮ Add the following:
import java.sql.*;
to access SQL related objects such as:
▮ ResultSet
▮ Statement
▮ Connection
▮ SQLException
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Result Sets
▮ All data is returned by a SQL select
statement as a ResultSet object
▮ A result set is comprised of a:
▮ Table that is comprised of
▮ Rows/records
▮ Columns/fields
▮ A pointer/cursor that is used to move
between the rows
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Result Sets
▮ Have a variety of methods to retrieve
field data
▮ getXXX(field identifier) - where XXX is
the data type (Int, String, etc.)
▮ Field can be identified by the field name or
the column number
▮ Column number more efficient
▮ Field name better for documentation
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Result Sets
▮ .next() increments pointer to next
row/record
▮ Initially pointer set before the first row, so
must .next() to “prime the read”
▮ Returns a Boolean value indicating whether
there is a record or not
▮ .previous(), .last()
▮ .relative(#) moves pointer # number of
rows
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Result Set & Choice Example
try {
stmt = conn.createStatement();
select = "SELECT School FROM Schools ORDER BY School";
rs = stmt.executeQuery(select);
while (rs.next()){
schoolsCB.addItem(rs.getString(1));
}
Populates Choice
stmt.close();
}
with school names
catch (SQLException sqlex) {
sqlex.printStackTrace();
System.out.println("\nSQL exception on query\n");
}
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Encapsulation
▮ Many terms used to describe:
▮ Transparency
▮ Information hiding
▮ Implementation ignorance
▮ Programmers have an “interface” to an
object with no idea of how it works
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Encapsulation
▮ Someone knows how to drive:
▮ Turn the key
▮ Step on gas pedal
▮ Steer
▮ Step on brake pedal
▮ The driver doesn’t have to know how
the car works or any of its internal
components
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Encapsulation
▮ Many methods and data are hidden
from the user/application
▮ Changes to the class (variables and
methods) do not affect users of the
class
▮ Data accessible only through publicly
defined methods
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Encapsulation
Getters
Constructors
DATA
Rules
chapter 10
Setters
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Encapsulation
▮ If programmers can’t directly access
the data, their applications can’t
screw it up!!
▮ PUBLIC methods comprise the
interface
▮ PRIVATE methods for internal
functions and non-user fields
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Encapsulate a File/Table
▮ Define a class for the file (ex. TransTable)
▮ In the class, define private variables for
each field in the file
▮ For each private variable:
▮ Define a getter method
▮ Define a setter with validation functions
▮ Define CRUD functions
▮ Define functions to return associated
objects (customer purchase orders)
▮ Define business functions (getTotal)
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Business Change
▮ Selling to schools via purchase orders
▮ Have a DB called Sales with a table called
TxTable
▮ Will create a new class to encapsulate
TxTable called TransTable
▮ Need a new frame to add PO sales info
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PO Sale
▮ Create a new POSale Frame to input PO
sale transaction info
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PO Sale
Creates
PO Sale
Sales
Info
TransTable
Sales
Info
Empty
Frame
Sales DB
Sales
Info
TxTable
User
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This new class will
eventually have all
these methods
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How to Encapsulate a File
▮ TransTable class will encapsulate the
TxTable file (with these fields)
▮ School – char 25
▮ Customer – char 30
▮ PurchDate – char 10
▮ ItemName – char 30
▮ Qty – long integer (4 bytes)
▮ Price – currency
▮ PayDate – char 10
▮ PONum – char 15
▮ Comments - memo
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© copyright Janson Industries 2011
▮ PaidAmt – currency
32
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How to Encapsulate a File
▮ Define a private variable for each field
import
import
import
import
java.util.*;
java.util.Date;
java.sql.*;
java.text.DateFormat;
Need to import various date
classes and the sql package
public class TransTable {
private String school;
private String customer;
private String purchDate;
private String itemName;
private int qty;
private double price;
private String payDate;
private String pONum;
private String comments;
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© copyright Janson Industries 2011
double paidAmt;
34
How to Encapsulate a File
private Date date = new Date();
private String currentDate;
DateFormat dfShort = DateFormat.getDateInstance(DateFormat.SHORT);
static Connection conn = null;
static String url = ("jdbc:odbc:Sales");
static Properties p = new Properties();
static String driver = ("sun.jdbc.odbc.JdbcOdbcDriver");
static PreparedStatement psAddTT = null;
static Statement stmt, updateStmt;
public String getSchool() {return school;}
public String getCustomer() {return customer;}
public String getPurchDate() {return purchDate;}
public String getItemName() {return itemName;}
public int getQty() {return qty;}
public double getPrice() {return price;}
public String getPayDate() {return payDate;}
public String getPONum() {return pONum;}
public String getComments() {return comments;}
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copyright Janson Industries 2011
public
double getPaidAmt()© {return
paidAmt;}
Need date variables/objects
Need DBMS
variables/objects
Create getters
35
How to Encapsulate a File
public void setQty(int qty) {
this.qty = qty;}
public void setPrice(double price) {
this.price = price;}
public void setComments(String comments) {
this.comments = comments;}
public void setPaidAmt(double paidAmt) {
this.paidAmt = paidAmt;}
public void setPurchDate() {
this.purchDate = String.valueOf(dfShort.format(date));}
public void setPayDate() {
this.payDate = String.valueOf(dfShort.format(date));}
Create setters (some with validation functions)
public void setSchool(String school) throws InvalidLengthException {
if (school.length() > 25)
throw new InvalidLengthException("School", school, 25);
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this.school = school;}
How to Encapsulate a File
public void setCustomer(String customer) throws InvalidLengthException {
if (customer.length() > 30)
throw new InvalidLengthException("Customer", customer, 30);
this.customer = customer;
}
public void setPONum(String pONum) throws InvalidLengthException {
if (pONum.length() > 15)
throw new InvalidLengthException("PO Number", pONum, 15);
this.pONum = pONum;
}
public void setItemName(String itemName) throws InvalidLengthException {
if (itemName.length() > 30)
throw new InvalidLengthException("Item Name", itemName, 30);
this.itemName = itemName;}
}
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© copyright Janson Industries 2011
Create and use
a new Exception subclass
37
InvalidLengthException class
public class InvalidLengthException extends Exception {
public InvalidLengthException(String field, String value, int
length)
{ super("The value entered for " + field + ": " + value +
", is too big. \nMax length is " + length + ".");
} // end of constructor for InvalidLengthException
/** \n command line control
*/
public static void main(String args[]) {
System.out.println("Welcome to class invalidLengthException");
} // end main
} // end of class InvalidLengthException
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CRUD
▮ We need functions to Create, Read,
Update and Delete transactions
▮ The create function is done with a
simple default constructor (a constructor
with no arguments)
public TransTable() {}
▮ When invoked, this creates a TransTable
object with all the private fields
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CRUD
▮ Of course, a calling program will have to
set all the values
▮ And a write function will have to be
executed to make the transaction info
persistent
▮ In addition, need connection variables in
order to do any reads/writes
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Application Probs
▮ We are executing the same SQL
statement many times
▮ Statement is translated into ML every time
executed
▮ Very inefficient
▮ Solution: PreparedStatement
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Prepared Statement
▮ A predefined/translated SQL statement
▮ Before executing, supply data for the
statement
▮ More efficient
▮ Already created the variable as follows :
static PreparedStatement psAddTT = null;
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Prepared Statement
▮ Need a prepared statement object
▮ Retrieved from the connection object
psAddTT = con.prepareStatement("INSERT INTO EXAMPLES." +
"CUSTMAST VALUES(?, ?, ?, ?)");
▮ Therefore need a connection object
▮ The ?’s “hold” the place for the data values
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init
private void init() {
if (conn == null) {
try {
Class.forName(driver);
p.put("naming", "sql");
p.put("user", "anonymous");
p.put("password", "guest");
conn = DriverManager.getConnection(url, p);
} catch (ClassNotFoundException e) {
System.out.println("couldn't find jdbc/odbc driver");
e.printStackTrace();
System.exit(1);
} catch (SQLException e) {
System.out.println("couldn't connect");
e.printStackTrace();
System.exit(1);
}
} chapter
}
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© copyright Janson Industries 2011
init creates connection to DB
44
init
try {
if (psAddTT == null) {
psAddTT = conn.prepareStatement("INSERT INTO "
+ "TxTable(School, Customer, PurchDate, ItemName, Qty,"
+ "Price, PONum, Comments, PaidAmt) VALUES(?, ?, ?, ?, ?, ?, ?, ?, ?)");
}
if (stmt == null) {
stmt = conn.createStatement();
}
if (updateStmt == null) {
updateStmt = conn.createStatement();
}
} catch (SQLException e) {
System.out.println("couldn't connect");
e.printStackTrace();
System.exit(1);
}
}
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...and creates the
statement objects
needed to access data
in the DB
Access a DB
▮ Need to call init from all constructors
▮ Change null constructor to run init
public TransTable() {init();}
▮ Time to test, add the following main
method and run as Java app
public static void main(String[] args) {
TransTable tt = new TransTable();
System.out.println("Created a TransTable object");
}
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46
Never defined the DB as an ODBC data source
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47
Click Start, Control Panel, Administrative Tools
Data Sources
(ODBC)
Click Add
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In Windows 10 - Start, Control Panel, System and
Security, Administrative Tools
ODBC Data Sources
Click Add
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Select Microsoft Access Driver and click Finish
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In Windows 10 - Select Microsoft Access Driver and
click Finish
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51
If Access Driver doesn’t appear and you are running
64 bit Win7, here are links on work around:
http://answers.microsoft.com/enus/office/forum/office_2007-excel/no-odbc-driversavailable-for-excel-or-access-in/001c234b-dfd5-4378a325-c4f1482fb6fd
http://stackoverflow.com/questions/6721702/windo
ws-7-64-bit-odbc-drivers-for-ms-access-missing
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Specify Sales and click Select
Locate and select the DB file then click OK
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Click OK
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Sales appears in Data Source list
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© copyright Janson Industries 2011
Click OK
55
Test again
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56
PO Sale
▮ Encapsulating TransTable will make
other classes (like POSale) that use the
DB simpler
▮ Created a new PO Sale Frame to capture
PO sale transaction info
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57
import
import
import
import
import
import
import
import
import
import
import
java.awt.Frame;
java.awt.event.ActionEvent;
java.awt.event.ActionListener;
java.awt.event.WindowEvent;
java.awt.event.WindowListener;
java.awt.Dimension;
java.awt.Label;
java.awt.Rectangle;
java.awt.TextField;
java.awt.Button;
java.awt.Point;
POSale
public class POSale extends Frame implements ActionListener,
WindowListener {
private
private
private
private
private
private
private
private
private
static final long serialVersionUID =
Button addBtn = null;
private
TextField custNameTF = null; private
TextField itemNameTF = null; private
TextField qtyTF = null;
private
TextField priceTF = null;
private
Label schoolLbl = null;
private
Label commentLbl = null;
private
TextField pONumTF = null;
private
chapter 10
1L;
Label custNameLbl = null;
Label itemNameLbl = null;
Label qtyLbl = null;
Label priceLbl = null;
Label resultLbl = null;
TextField schoolTF = null;
TextField commentsTF = null;
Label pONumLbl = null;
Visual components
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58
public void windowActivated(WindowEvent e) {}
public void windowClosed(WindowEvent e) {}
public void windowClosing(WindowEvent e) {
this.dispose();}
public void windowDeactivated(WindowEvent e) {}
public void windowDeiconified(WindowEvent e) {}
public void windowIconified(WindowEvent e) {}
public void windowOpened(WindowEvent e) {}
Window Listener
methods
private Button getAddBtn() {
if (addBtn == null) {
addBtn = new Button();
addBtn.setLabel("Add");
addBtn.setLocation(new Point(237, 178));
addBtn.setSize(new Dimension(60, 23));
addBtn.addActionListener(this);
}
return addBtn;
}
Visual component
getters
private TextField getCustNameTF() {
if (custNameTF == null) {
custNameTF = new TextField();
custNameTF.setBounds(new Rectangle(147, 45, 140, 23));
}
return custNameTF;
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© copyright Janson Industries 2011
}
59
private TextField getItemNameTF() { if (itemNameTF == null) {
itemNameTF = new TextField();
itemNameTF.setBounds(new Rectangle(147, 78, 140, 23));}
return itemNameTF; }
private TextField getQtyTF() { if (qtyTF == null) {
qtyTF = new TextField();
qtyTF.setBounds(new Rectangle(108, 111, 32, 23)); }
return qtyTF; }
private TextField getPriceTF() { if (priceTF == null) {
priceTF = new TextField();
priceTF.setBounds(new Rectangle(199, 111, 60, 23)); }
return priceTF;}
private TextField getSchoolTF() { if (schoolTF == null) {
schoolTF = new TextField();
schoolTF.setBounds(new Rectangle(389, 45, 113, 23)); }
return schoolTF;}
Remaining visual
component
getters
private TextField getCommentsTF() { if (commentsTF == null) {
commentsTF = new TextField();
commentsTF.setBounds(new Rectangle(389, 79, 113, 55));}
return commentsTF;}
private TextField getPONumTF() { if (pONumTF == null) {
pONumTF = new TextField();
pONumTF.setBounds(new Rectangle(331, 111, 47, 23)); }
return
pONumTF;}
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10
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60
public POSale() {
super();
initialize();
}
Null constructor
that
calls
initialize
Sale
private void initialize() {
Defines labels, then frame
pONumLbl = new Label();
pONumLbl.setBounds(new Rectangle(265, 111, 62, 23));
pONumLbl.setText("PO Num:"); commentLbl = new Label();
commentLbl.setBounds(new Rectangle(307, 78, 71, 23));
commentLbl.setText("Comments:");
schoolLbl = new Label();
schoolLbl.setBounds(new Rectangle(325, 45, 53, 23));
schoolLbl.setText("School: "); resultLbl = new Label();
resultLbl.setBounds(new Rectangle(14, 145, 508, 23));
resultLbl.setAlignment(Label.CENTER);
resultLbl.setText("");
priceLbl = new Label();
priceLbl.setBounds(new Rectangle(147, 111, 45, 23));
priceLbl.setText("Price:");
qtyLbl = new Label();
qtyLbl.setBounds(new Rectangle(39, 111, 45, 23));
qtyLbl.setText("Quantity:"); itemNameLbl = new Label();
itemNameLbl.setBounds(new Rectangle(61, 78, 79, 23));
itemNameLbl.setText("Item Name:");
custNameLbl = new Label();
custNameLbl.setBounds(new Rectangle(31, 45, 109, 23));
custNameLbl.setText("Customer Name:");
this.setLayout(null);
this.setSize(535, 214);
this.setTitle("PO Sale");
this.setVisible(true);
this.add(getAddBtn(), null); this.add(custNameLbl, null);
this.add(getCustNameTF(), null);
this.add(itemNameLbl, null);
this.add(getItemNameTF(), null);
this.add(qtyLbl, null);
this.add(getQtyTF(), null);
this.add(priceLbl, null);
this.add(getPriceTF(), null);
this.add(resultLbl, null);
this.add(schoolLbl, null);
this.add(getSchoolTF(), null);
this.add(commentLbl, null);
this.add(getCommentsTF(), null);
this.add(getPONumTF(), null); this.add(pONumLbl, null);
addWindowListener(this);
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}
Sale
▮ And a main to test
public static void main(String[] args) {
new POSale();
}
▮ Speaking of test, code an actionPerformed to:
▮ Create a TransTable object
▮ Populate the object with info entered in
Frame
▮ Clear the frame text fields
▮ Display info from TransTable object
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public void actionPerformed(ActionEvent e) {
TransTable newSale = new TransTable();
try {
newSale.setCustomer(custNameTF.getText());
newSale.setSchool(schoolTF.getText());
newSale.setPONum(pONumTF.getText());
newSale.setItemName(itemNameTF.getText());
newSale.setPrice(Double.valueOf(priceTF.getText()).doubleValue());
newSale.setComments(commentsTF.getText());
newSale.setQty(Integer.valueOf(qtyTF.getText()).intValue());
newSale.setPurchDate();
custNameTF.setText(""); schoolTF.setText("");
pONumTF.setText("");
priceTF.setText("");
commentsTF.setText(""); qtyTF.setText("");
itemNameTF.setText("");
System.out.println("Successfully created a TransTable object for PO
Num:" + newSale.getPONum());
}
Creates newSale,
retrieves info from
frame, sets props
Clears TFs
catch (InvalidLengthException err)
{
System.out.println("\nLength exception: \n"+err.getMessage());
}
}
Proves object exists by displaying PO Num
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Run POSale, enter a PO Num, click Add
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64
Success!
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65
PO Sale
▮ Might be nice if we put the info in the
database table
▮ Need to finish CRUD functions in
TransTable
▮ PO Sale will invoke the U of CRUD
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66
Prepared Statement
▮ In TransTable, before the insert can be
performed, must supply values to the
prepared statement:
psAddTT.setString(1, School);
psAddTT.setString(2, CustName);
psAddTT.setString(3, PurchDate);
:
:
:
psAddTT.executeUpdate();
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Prepared Statement
▮ Of course, the variables CustName, etc.
had to be set to some values
▮ POSale does this after it creates the
TransTable object (newSale)
newSale.setSchool(schoolTF.getText());
newSale.setCustName (custNameTF.getText());
newSale.setPurchDate();
:
:
:
:
:
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68
Update (in TransTable)
public void write() {
try {
psAddTT.setString(1, school);
psAddTT.setString(2, customer);
psAddTT.setString(3, purchDate);
psAddTT.setString(4, itemName);
psAddTT.setInt(5, qty);
psAddTT.setDouble(6, price);
psAddTT.setString(7, pONum);
psAddTT.setString(8, comments);
psAddTT.setDouble(9, 0);
psAddTT.executeUpdate(); }
Sets paid amount to zero
catch (SQLException e) {
System.err.println("General SQL exception.");
System.err.println(e.getMessage()); }
chapter}10
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POSale must invoke write in actionPerformed
Put out a user msg and comment out the test println
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PO Sale
▮ Notice that POSale doesn’t worry about
connections.
▮ There are no:
▮ Drivers
▮ Driver managers
▮ Connection objects
▮ Prepared statements
▮ Encapsulating the file makes the client
class’ logic/coding simpler!!
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Now when we run POSale, enter info, & click Add…
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…the info is inserted into the table
chapter 10
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Paying a PO
▮ Need the ability to mark a PO as paid
▮ New POPay frame will:
▮ Display a list of outstanding PO's with PO #,
school, and date
▮ When user selects a PO, POPay (using the
TransTable object) updates pay date and paid
amt
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Paying a PO
dummyTT
Creates
TransTable
POPay
Outstanding
POs
Frame
w/ POs
PO’s where
paidAmt = 0
Sales DB
User
Chapter 10
TransTable
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75
For each unpaid PO display PO#, School & PO Date
When you click on one...
chapter 10
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...the PayDate and PaidAmt are updated...
chapter 10
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77
Paying a PO
2
Creates
w/ selected PO #
POPay
realPO
Pay
4
Selected
PO
User
Chapter 10
1
3
TransTable
Select PO
info
Paid date
& amount
Sales DB
TransTable
5
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78
read(String whereClause)
▮ There can be many read functions:
▮ A read for a key value (a single record)
▮ A read for all records in a table
▮ A read for records based on a condition
▮ Therefore the actual read method needs
to accept a where clause
▮ Other methods need to create the where
clause and pass to read()
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read(String whereClause)
▮ Because the SQL read statement will be
dynamically built can't use a prepared
statement
▮ Must use a regular statement object
▮ That's why we created a variable
private Statement stmt;
▮ And in init, created the statement object
stmt = conn.createStatement();
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TransTable(String poNum)
▮ To retrieve a single record, create a
constructor that accepts a key value
▮ Will build read to retrieve records based
on a Where condition, so need a method
to pass a null Where
▮ POPay only wants outstanding PO's
▮ Need a method to pass a where clause that
has the condition paid amount = 0
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read(String whereClause)
▮ The select statement simply returns a
result set
▮ TransTable needs to:
▮ Assign the result set to a result set variable
▮ Retrieve data from the result set and set the
TransTable object properties
▮ read method will assign result set
▮ Will create a getDataFromRS method to
get data and assign to properties
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Read
read accepts a where clause
if the where clause is blank, will retrieve all records
private ResultSet rs;
:
:
:
:
private void read(String whereClause) {
try {
String select = "SELECT * FROM TxTable " +
whereClause;
rs = stmt.executeQuery(select);
rs.next();
} catch (SQLException sqlex) {
sqlex.printStackTrace();
System.out.println("\nSQL exception on Select\n");
}
© copyright Janson Industries 2011
}chapter 10
"Priming read"
83
Single Record Read
Invokes the null constructor – why?
public TransTable(String ponum) {
this();
try {
this.read(" WHERE PONum = '" + ponum + "'");
this.getDataFromRS();
rs.close();
stmt.close();
} catch (SQLException e) {
System.out.println("SQL exceptions");
e.printStackTrace();
System.exit(1);
}
}
Builds where clause, executes
read & getDataFromRS
House cleaning, closes rs and statement
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getDataFromRS
private void getDataFromRS() {
try { school = rs.getString(1);
customer = rs.getString(2);
purchDate = rs.getString(3);
itemName = rs.getString(4);
qty = rs.getInt(5);
price = rs.getDouble(6);
payDate = rs.getString(7);
pONum = rs.getString(8);
comments = rs.getString(9);
paidAmt = rs.getDouble(10);
}
catch (SQLException sqlex) {
sqlex.printStackTrace();
System.out.println("\nSQL exception on rs get\n");
}chapter
} 10
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Other methods needed
▮ Still need:
▮ A delete function (not going to show/do)
▮ A getAll method
▮ Related business functions
▮ getOutStandingPOs method
▮ pass where clause of paidAmt = 0
▮ setPOPaid method
▮ Then must create POPay
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Get all POs
▮ Passes a null where clause so all POs will be
returned
▮ Pretty simple but notice it returns a result set
public ResultSet getAllPOs()
{
if (conn==null) { init();}
read("");
return rs;
}
▮ This means the invoking object must handle
the result set
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Outstanding POs
▮ Again, pretty simple but it also returns a result set
public ResultSet getOutStandingPOs()
{
if (conn==null) { init();}
read(" WHERE PaidAmt = 0");
return rs;
}
▮ This means the invoking object (POPay) must
handle the result set
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Outstanding POs
▮ Will test with following main method
public static void main(String[] args) {
TransTable tt = new TransTable();
ResultSet rsTest = tt.getOutStandingPOs();
try {
System.out.println("Got the first PO " +
rsTest.getString(8));
} catch (SQLException sqlex) {
sqlex.printStackTrace();
System.out.println("SQL exception on rs get");
}
}
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Updating (in TransTable)
▮ Need to update just the PayDate and
PaidAmt fields
▮ Needed another statement variable
private Statement updateStmt;
▮ In init, created & assigned statement object
updateStmt = conn.createStatement();
▮ Then create two new methods:
▮ One to build the SQL update statement
▮ One to perform the update
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Updating (in TransTable)
public void setPOPaid() {
this.setPayDate();
String totalCost = String.valueOf(qty * price);
String update = "Update TxTable Set PayDate = '" +
this.payDate + "', PaidAmt = " +
totalCost + “ WHERE PONum = '" +
this.pONum + "'";
this.update(update);
}
public void update(String sqlupdate) {
try {
updateStmt.executeUpdate(sqlupdate);
}
catch (SQLException e) {
System.err.println("General SQL exception.");
System.err.println(e.getMessage());
}
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}
92
POPay Frame
▮ Initially will display all outstanding POs
▮ User selects one
▮ POPay then:
▮ Creates a new TransTable object for the
selected PO
▮ Invokes the setPOPaid method
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Assuming we have the data above
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For each unpaid PO display PO#, School & PO Date
When you click on one...
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...message displayed and list box cleared…
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...the PayDate and PaidAmt are updated
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Running again would show that the PO was updated
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POPay Frame
import
import
import
import
import
java.awt.Frame;
java.awt.event.ItemListener;
java.awt.event.WindowListener;
java.sql.SQLException;
java.awt.Rectangle;
import
import
import
import
import
java.awt.event.ItemEvent;
java.awt.event.WindowEvent;
java.sql.ResultSet;
java.awt.List;
java.awt.Label;
public class POPay extends Frame implements WindowListener, ItemListener
{
private static final long serialVersionUID = 1L;
ResultSet rs;
private List outstandingPOLB = null;
private Label label = null;
2 visual comps (list &
label) & a result set
public void windowActivated(WindowEvent e) {}
public void windowClosed(WindowEvent e) {}
public void windowClosing(WindowEvent e) {
this.dispose();
}
public void windowDeactivated(WindowEvent e) {}
public void windowDeiconified(WindowEvent e) {}
public void windowIconified(WindowEvent e) {}
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© copyright Janson Industries 2011
public
void windowOpened(WindowEvent
e) {}
Window
listener
methods
99
POPay Constructor
public POPay() {
super();
TransTable dummyTT = new TransTable();
rs = dummyTT.getOutStandingPOs();
initialize();
}
Creates a TransTable object
and retrieves outstanding POs
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Initialize (in POPay)
private void initialize() {
label = new Label();
label.setBounds(new Rectangle(5, 141, 291, 23));
label.setAlignment(Label.CENTER);
label.setText("Select the PO to be paid");
this.setLayout(null);
this.setSize(300, 200);
this.setTitle("Pay a PO");
Defines label and
frame and gets the list
this.setVisible(true);
this.add(getOutstandingPOLB(), null);
this.add(label, null);
addWindowListener(this);
}
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List (in POPay)
▮ Need to add outstanding PO's to the list
▮ Tie an item listener to the list
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List (in POPay)
RAD generates code to create, size and position
private List getOutstandingPOLB() {
if (outstandingPOLB == null) {
outstandingPOLB = new List();
outstandingPOLB.setBounds(new Rectangle(35, 66, 229, 64));
outstandingPOLB.addItemListener(this);
try {
do {
outstandingPOLB.add(rs.getString(8) +
" " + rs.getString(1) +
" " + rs.getString(3));
} while (rs.next());
} catch (SQLException e) {
e.printStackTrace();
}
}
return outstandingPOLB;
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© copyright Janson Industries 2011
}
Programmer adds listener &
loop to retrieve PO info from
result set & add to list
103
POPay
▮ This is a good time to test that:
▮ Connection works
▮ All outstanding POs are displayed
public static void main(String[] args) {
POPay pay = new POPay();
}
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Looking good!
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Item State Changed
▮ itemStateChanged method must:
▮ Retrieve the selected item from LB
▮ Extract the PO # from the selected item
▮ Create a TransTable object for the PO #
▮ Invoke setPOPaid
▮ Clear the list
▮ Display the paid message
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public void itemStateChanged (ItemEvent e) {
String selectedPO = outstandingPOLB.getSelectedItem();
int index = 0;
Retrieve PO info, get first char, assign to PO#
String pONum =
String.valueOf(selectedPO.charAt(index));
index++;
Point to next char
while(!(String.valueOf(selectedPO.charAt(index)).
equals(" "))) {
pONum = pONum +
String.valueOf(selectedPO.charAt(index));
index++;
Loop through till a space is encountered –
}
space means end of the PO# reached
TransTable realPO = new TransTable(pONum);
realPO.setPOPaid(); Create TransTable and invoke setPOPaid
label.setText("PO# " + realPO.getPONum() + " paid");
outstandingPOLB.removeAll();
}
Build and display
message and clear POs from list
© copyright Janson Industries 2011
chapter 10
107
Run and select PO # 82634
To verify:
Check that PayDate and PaidAmt are updated
Run again and only 2 POs should be shown
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Enterprise Data
▮ Rarely use MS Access to store sizable
amount of data
▮ Can consist of many DBs with many
tables
▮ Thousands of tables not unusual
▮ Tables stored and possibly moved
between different types of DBMS:
▮
▮ DB2, Oracle, SQL Server, ...
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Enterprise Data
▮ Defining connection info and objects in
each "encapsulating" (i.e. table/file) class
redundant
▮ Takes up more space
▮ Longer to make changes
▮ Greater chance of error when making
changes
▮ Inheritance can help!
▮
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Inheritance
▮ By creating superclasses, we can reduce
the amount of duplicate code
▮ For instance, all the connection variables
and methods:
▮ variables (url, password, driver, etc.)
▮ conn
▮ init
▮ Define in one DBMS-type superclass and
have table/file classes inherit them
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Abstract types
▮ A subclass (or implementing class) must
have methods with the same signature
as its superclass' abstract methods
▮ E.g. abstract methods are "behind" the
WindowListener methods
▮ All those methods you were forced to code,
are defined as abstract methods in the
WindowListener class
▮ A class can also be defined as abstract
▮ abstract classes cannot be instantiated
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Inheritance
▮ Remember the steps to encapsulate a file:
▮ Define a class for the file
▮ Define private variables for each field in the
file
▮ Define a getter and setter for each private
variable
▮ Define CRUD functions
▮ Define functions to return associated objects
(getOutStandingPOs())
▮ Define business functions (setPOPaid())
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Inheritance
▮ We can enforce consistency across all
the encapsulating classes by creating
“abstract” methods that define the
encapsulation interface method’s
signatures in a superclass
▮ I.e. define abstract CRUD methods in the
superclass so that all subclasses must code
CRUD methods the same way
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Multiple DBMS Example
▮ DBFile class will define:
▮ Common variables and functions
▮ Abstract standard interface methods
▮ Individual DBMS classes define:
▮ Unique values for that DBMS type
▮ Individual Table classes define:
▮ Unique values for the table
▮ Standard interface methods
▮
Unique
functions
for
that
table
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Multiple DBMS Example
DBFile
conn, url, driver, user, pw, etc.
private init();
abstract delete(),write(), update(), read()
is a
is a
AccessFile
DB2File
OracleFile
driver = ("sun.
jdbc.odbc.
JdbcOdbcDriver")
user =
pw =
driver = ("com.
ibm.as400.access
.AS400JDBCDriver")
user =
pw =
driver= “oracle
.jdbc.driver.
OracleDriver”)
user =
pw =
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Database Example
▮ We’ll create an abstract DBFile class to…
▮ Define connection variables
// DBFile
Abstract classes
import java.util.*;
import java.sql.*;
cannot be
abstract class DBFile {
instantiated!!
Connection conn = null;
String url = null;
String user, pw;
Properties p = new Properties();
String driver = null;
public boolean connExists = false;
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Database Example
▮ … and to…
▮ Create a common connection method init
public void init() { if (conn == null) { try {
Class.forName(driver); p.put("naming", "sql");
p.put("user", user); p.put("password", pw);
conn = DriverManager.getConnection(url, p);
} catch (ClassNotFoundException e) {
System.out.println("couldn't find driver");
e.printStackTrace(); System.exit(1);
} catch (SQLException e) {
System.out.println("couldn't connect");
e.printStackTrace(); System.exit(1); } } }
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Database Example
▮ … and to:
▮ Enforce CRUD
protected
protected
protected
protected
protected
abstract
abstract
abstract
abstract
abstract
void
void
void
void
void
write();
update(String sqlStmt);
read(String whereClause);
delete(String sqlStmt);
getDataFromRS();
}
▮ Protected allow subclasses access
▮ Even if in a different package
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119
Database Example
▮ You can have many different types of
databases at many different locations
▮ Local Access DB’s
▮ Remote Oracle DB’s
▮ Remote DB2 DB’s
▮ Need subclasses to define each “type” of
DB’s (or multiple DBMS of same type on
different machines) unique connection
values
▮ Driver, URL, PW, ID
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AccessFile Class
abstract class AccessFile extends DBFile {
public AccessFile () {
url = "jdbc:odbc:Sales";
driver = "sun.jdbc.odbc.JdbcOdbcDriver";
user = "anonymous";
pw = "guest";
}
}
Also defined as abstract classes
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DB2File Class
▮ Have to get the correct driver
▮ JTOpen available (on website) or free at:
▮ http://sourceforge.net/projects/jt400/files/JT
Open-full/7.3/jtopen_7_3.zip/download
// DB2File
abstract class DB2File extends DBFile {
public DB2File() {
url = "jdbc:as400://207.203.206.4/Sales";
driver = "com.ibm.as400.access.AS400JDBCDriver";
user = "bjanson";
pw = "jeter"; }
}
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Oracle File Class
▮ Have to get the correct driver
▮ OracleDriver on website or free at:
▮ http://www.oracle.com/technology/software/
tech/java/sqlj_jdbc/index.html
// Oracle File
abstract class OracleFile extends DBFile {
public OracleFile() {
url = "jdbc:oracle:thin:@207.203.206.4:1521:SID";
driver = "oracle.jdbc.driver.OracleDriver";
user = "bjanson";
pw = "jeter"; }
}
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123
Database Example
DBFile
public init();
abstract delete,
write, update, read
is a
AccessFile
driver =
user =
pw =
is a
TransTable
chapter 10
is a
Customer
© copyright Janson Industries 2011
124
TransTable Changes
▮ TransTable is a subclass of AccessFile and
AccessFile variables are inherited
▮ TransTable doesn’t define init() or variables
(i.e. url) instead inherits from DBFile
import java.util.*;
:
:
:
public class TransTable extends AccessFile {
:
:
:
:
//static Connection conn = null;
//static String url = ("jdbc:odbc:Sales");
//static Properties p = new Properties();
//static String driver = ("sun.jdbc.odbc.JdbcOdbcDriver");
//private String userid = new String("student99");
//private String pw = new String("pinrut");
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125
TransTable Changes
▮ Comment out old init
▮ Must still run init (inherited init) and create
various statement objects
public TransTable() {
init();
try {
if (psAddTT == null) {
psAddTT = conn.prepareStatement("INSERT INTO "
+ "TxTable(School, Customer, PurchDate, ItemName, Qty,"
+ "Price, PONum, Comments, PaidAmt) VALUES(?, ?, ?, ?, ?, ?, ?, ?, ?)");
}
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TransTable Changes
if (stmt == null) {
stmt = conn.createStatement();
}
if (updateStmt == null) {
updateStmt = conn.createStatement();
}
} catch (SQLException e) {
System.out.println("couldn't connect");
e.printStackTrace();
System.exit(1);
}
}
protected void getDataFromRS() {...
protected
chapter
10
void read(String
whereClause)
© copyright Janson
Industries 2011 {...
127
TransTable Class
▮ Have a small problem with TransTable:
we never defined a delete method
▮ This is the error message when you don’t
code a required abstract method:
▮ What should you do?
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128
Verify that POPay still works
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129
TransTable Class
▮ If we moved TxTable from
Access to DB2 on an IBM
Power System…
▮ …just change TransTable to
extend DB2File
DBFile
public init();
abstract delete,
write, update, read
is a
DB2File
url=
driver =
user =
pw =
is a
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© copyright Janson Industries 2011
TransTable
130
TransTable DB2 Class
// TransTable.java
import java.sql.*;
public class TransTable extends DB2File{
private Statement stmt;
No communication
variables to change
public TransTable() {
init();....}
protected void delete(String whereClause) { }
“Got around” abstract delete method
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131
TransTable Class
▮ If we moved TxTable from
DB2 on an IBM Power
System to Oracle…
▮ …just change TransTable to
extend OracleFile
DBFile
public init();
abstract delete,
write, update, read
is a
OracleFile
url=
driver =
user =
pw =
is a
chapter 10
© copyright Janson Industries 2011
TransTable
132
TransTable DB2 Class
// TransTable.java
import java.sql.*;
public class TransTable extends OracleFile{
private Statement stmt;
No communication
variables to change
public TransTable() {
init();....}
protected void delete(String whereClause) { }
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133
TxTable DB2 Table
CREATE TABLE sales.txtable
(school
char(25),
customer
char(30),
purchdate
char(10),
qty
int,
itemname
char(30),
price
double,
paydate
char(10),
ponum
char(15),
comments
char(100),
paidamt
double)
chapter 10
Assuming the table
was created using
this SQL
© copyright Janson Industries 2011
134
TransTable Class
protected void read(String whereClause) {
try {
String select = "SELECT * FROM TxTable" + whereClause;
rs = stmt.executeQuery(select);
rs.next();
} catch (SQLException sqlex) {
sqlex.printStackTrace();
System.out.println("\nSQL exception on Select\n");
}
}
Do table classes or methods have any
idea TxTable was moved?
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135
DB2 Table
▮ DB2 driver must be downloaded
▮ jtopen folder on class website
▮ To run in RAD, driver must be added
to Java Build Path
▮ Right click project and select properties
▮ Select Java Build Path
▮ Click Libraries tab
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136
Click Add External Jars...
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137
Drill down to the jtopen/lib folder and select jt400.jar
Click Open then OK
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© copyright Janson Industries 2011
138
jt400.jar added to project
chapter 10
© copyright Janson Industries 2011
139
Run POSale, input a new PO
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© copyright Janson Industries 2011
140
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141
DB2 Table
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142
DB Problems
▮ If you get a Unhandled exceptions msg:
Unhandled exception
Type=Segmentation error vmState=0x00040000
J9Generic_Signal_Number=00000004 ExceptionCode=c0000005 ExceptionAddress=738B72D7 ContextFlags=0001003f
Handler1=7FEFA0C0 Handler2=7FECC180 InaccessibleAddress=00000000
EDI=00000000 ESI=70B52000 EAX=00000000 EBX=00000000
ECX=00000020 EDX=00000000
EIP=738B72D7 ESP=6F77DDD4 EBP=6F77DDD8 EFLAGS=00010202
GS=0000 FS=003B ES=0023 DS=0023
Module=C:\Windows\WinSxS\x86_microsoft.vc80.crt_1fc8b3b9a1e18e3b_8.0.50727.4927_none_d08a205e442db5b5\MSVCR80.dll
Module_base_address=738A0000 Offset_in_DLL=000172d7
Target=2_40_20110401_055940 (Windows 7 6.1 build 7600)
CPU=x86 (8 logical CPUs) (0xcf5d5000 RAM)
----------- Stack Backtrace ----------_strnicmp+0x7c (0x738B72D7 [MSVCR80+0x172d7])
_strnicmp+0xe9 (0x738B7344 [MSVCR80+0x17344])
(0x713042BE [ACECORE+0x42be])
--------------------------------------JVMDUMP006I Processing dump event "gpf", detail "" - please wait.
JVMDUMP032I JVM requested System dump using 'K:\JavaBookWS\CE\core.20110331.160455.6620.0001.dmp' in response to an even
JVMDUMP010I System dump written to K:\JavaBookWS\CE\core.20110331.160455.6620.0001.dmp
JVMDUMP032I JVM requested Snap dump using 'K:\JavaBookWS\CE\Snap.20110331.160455.6620.0002.trc' in response to an event
JVMDUMP010I Snap dump written to K:\JavaBookWS\CE\Snap.20110331.160455.6620.0002.trc
JVMDUMP032I JVM requested Java dump using 'K:\JavaBookWS\CE\javacore.20110331.160455.6620.0003.txt' in response to an event
JVMDUMP010I
Java dump written to K:\JavaBookWS\CE\javacore.20110331.160455.6620.0003.txt
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144
JVMDUMP013I Processed dump event "gpf", detail "".
Dumps can be accessed from within RAD
chapter 10
© copyright Janson Industries 2011
145
DB Problems
▮ Open the “dump” text file and scroll
down to find the stack trace
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© copyright Janson Industries 2011
146
Access Assg
▮ On the class web site is an Access DB
called TNTDB that you can download
▮ TNTDB has 2 tables
▮ employee (with employee 111)
▮ shipment
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147
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148
The tables are defined as follows:
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149
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150
Access Assg
▮ You’ll need to:
▮ Download the DB
▮ Define the DB as an ODBC data source
▮ Define the
▮ driver as sun.jdbc.odbc.JdbcOdbcDriver
▮ URL as jdbc:odbc:TNT Database
▮ userid as anonymous
▮ password as guest
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DB2 Assg
▮ At PLEIONE.SEALINC.ORG is a DB2
database/schema on an IBM Power
System called TNTDB
▮ TNTDB has 2 tables
▮ Employee (has emps 111, 222, 333)
▮ Shipment (has 7, 111, 8888)
▮ Your UserID is student99, and PW is
pinrut
▮ Don’t forget about the driver!!
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Shipment defined as above
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Oracle Assg
▮ Can only be accessed from on-campus!
▮ Must use driver ojdbc14.zip on class website
▮ Define URL as:
jdbc:oracle:thin:@stora:1521:sora10
▮ In SQL, don’t reference TNTDB
▮ Employee (has one emp, 999)
▮ Shipment (has one shipment, 999)
▮ Your UserID is Scott, and PW is TIGER
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