交通大學資訊工程學系
蔡文能
交通大學資訊工程學系 tsaiwn@csie.nctu.edu.tw

Java
Extend your JDK and JRE
Introduction to ODBC and JDBC
JDBC Drivers
JDBC Statements

Statement

PreparedStatement

CallableStatement
ResultSet
CORBA again
交通大學資訊工程學系 蔡文能
JDBC
第2頁

Java
JDBC
把 所有 class 都壓縮到一個 .jar 檔案 ( 名稱隨意 , 但不要與現有的重複 )
例如 : jar cvf myutilabc.jar M*.class So*.class
( 也可用 WINZIP 壓成 ZIP 檔再 rename 成 .jar 檔 )
把壓好的 .jar 檔 copy 到 你 JDK 根目錄下的 \jre\lib\ext\ 即可
 注意 .jar 檔中的目錄樹要與各 class 宣告的 package 相符合
 就是說不可以欺騙 Java compiler 與 Interpreter (JVM)
 可用 jar tvf your.jar
看看 ( 或用 WINZIP 看 )
 打 jar 看看 help
這樣 javac MyClass.java 編譯 或 java MyClass 執行 就都不用指定 classpath
 若不是放 JDK 的 \jre\lib\ext\ 中 , 則要指定 .jar 檔為你的 classpath javac -classpath ./mydir/myutil.jar; MyTest.java
java -classpath ./mydir/myutil.jar; MyTest
( 注意 分號不能省 ; 可以多個 jar 檔用 ; 分開 , 也可為目錄 )
交通大學資訊工程學系 蔡文能 第3頁

Java
RMI
JDBC CORBA
JDBC java.net
TCP/IP
交通大學資訊工程學系 蔡文能
Network
Copyright © 1997 Alex Chaffee 第4頁

Java JDBC
Most popular form of database system is the Relational
DataBase System. ( invented by Dr. E.F.Codd
)
Examples: Oracle, Sybase, IBM DB2, MS Sequel Server, MS
Access. ( Informix 已在 2001 年被 IBM 併購 )
Structured Query Language (SQL) is used among relational databases to construct queries.
These queries can be stand-alone or embedded within applications. This form of SQL is known as embedded SQL.
2001年7月2日，IBM公司順利完成斥資10億美元對Informix公司的資料庫
資產的收購。 IBM公司因此成為世界最大的中介軟體(MiddleWare)供應商 。
交通大學資訊工程學系 蔡文能 第5頁

Java JDBC
Invented by Dr. E.F.Codd.
data stored in records which live in tables
Multiple tables .
Each table is associated with a list of fields.
Each field (column) has a name , and type .
Each table is made up of a number of records ( rows ).
Each row contains the values for each field .
“Relation” (as in “Relational”) means row to column (not table to table) 列對欄位的關係 ; 注意不是表格對表格 !
交通大學資訊工程學系 蔡文能 第6頁

Java
JDBC
ODBC (Open Database Connectivity) is a Microsoft standard from the mid 1990’s.
ODBC standard is an interface by which application programs can access and process SQL databases in a DBMS-independent manner. It contains:

A Data Source that is the database, its associated DBMS, operating system and network platform

A DBMS Driver that is supplied by the DBMS vendor or independent software companies

A Driver Manager that is supplied by the vendor of the O/S platform where the application is running. ( 例如 MicroSoft 提供 Windows 的 )
It requires an ODBC driver to be provided for each database system from which you want to manipulate data.
交通大學資訊工程學系 蔡文能 第7頁

Java JDBC
Application
Class1 Class2
ODBC
DriverType1
Driver Manager
DriverType2 DriverType3
DataSource3
DataSource1
交通大學資訊工程學系 蔡文能
DataSource2
第8頁

Java JDBC
When applications written in Java want to access data sources, they use classes and associated methods provided by Java DBC (JDBC) API.
JDBC is specified an an
“ interface
”
.
An interface in Java can have many
“ implementations
”
.
So it provides a convenient way to realize many
“ drivers
”
JDBC is implemented via classes in the java.sql
package
交通大學資訊工程學系 蔡文能 第9頁

Java JDBC
Java supports embedded SQL .
Also it provides an JDBC API as a standard way to connect to common relational databases.
You need a JDBC:ODBC bridge for using the embedded SQL in Java.

Other JDBC Drivers are available for some RDBMS java.sql package and an extensive exception hierarchy.
交通大學資訊工程學系 蔡文能 第10頁

Java JDBC
SQL was initiated by IBM as part of its System R research prototype in the late 1970s
There are many different types of SQL commands (SELECT,
INSERT, UPDATE, DELETE, …).
For example: to create a new record:
"INSERT INTO password (Name, Password) VALUES ('Dave', 'blah')"
Reference:
A guide to SQL standard –
4th Edition. CJ Date & Hugh Darman. Addison Wesley. 1997.
http://www.opengroup.org/public/tech/datam/sql.htm
交通大學資訊工程學系 蔡文能 第11頁

Java
JDBC
SELECT column1, column2, ..., columnN
FROM table1 [, table2, ..., tableN ]
[WHERE clause] column# are the field names.
table# are table names.
The WHERE clause can restrict the rows used to determine the result.
交通大學資訊工程學系 蔡文能 第12頁

Java JDBC
INSERT INTO table ( field1, field2 )
VALUES ( value1, value2 )
 inserts a new record into the named table
UPDATE table SET ( field1 = value1, field2
= value2 ) WHERE condition
 changes an existing record or records
DELETE FROM table WHERE condition
 removes all records that match condition
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第13頁

Java JDBC
SQL
Direct SQL (= ad-hoc SQL) is rarely used

Also know as interactive SQL (iSQL)
In practice: SQL is embedded in some application code
 user interaction, devices, programming logic
SQL code is enbedded using special syntax into a host language (C, Java, etc.)
交通大學資訊工程學系 蔡文能 第14頁

Java
交通大學資訊工程學系 蔡文能
JDBC
第15頁

Java JDBC
Client
E.g. a
Java Applet
Middle
Ware
IDL
Middle
Ware
Server
E.g. DBMS
IDL
Network
Internet (TCP/IP)
IDL = Interface Definition Language
交通大學資訊工程學系 蔡文能 第16頁

Java JDBC
Driver Manager : Loads database drivers, and manages the connection between application & driver.
Driver : Translates API calls to operations for a specific data source.
Connection : A session between an application and a driver.
Statement : A SQL statement to perform a query or an update operation.
Metadata : Information about the returned data, driver and the database.
Result Set : Logical set of columns and rows returned by executing a statement.
交通大學資訊工程學系 蔡文能 第17頁

Java
JDBC
Java supports DB facilities by providing classes and interfaces for its components
DriverManager class
Connection interface (abstract class)
Statement interface (to be instantiated with values from the actual SQL statement)
ResultSet interface

ResultSet = the records returned from a SQL Statement
JDBC is implemented via classes in the java.sql
package
交通大學資訊工程學系 蔡文能 第18頁

Java JDBC
交通大學資訊工程學系 蔡文能 第19頁

Java
JDBC
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第20頁

Java
JDBC
Phase Task Relevant java.sql classes
Initialisation
Processing
Load driver
Create connection
DriverManager
Connection
Generate SQL statements
Process result data
Statement
ResultSet etc.
Termination
交通大學資訊工程學系 蔡文能
Terminate connection
Release data structures
Connection
Statement etc.
第21頁

Java
All JDBC programs do the following:
 1
) load the JDBC driver
 2 ) Specify the name and location of the database being used
 3
) Connect to the database with a
Connection object

4) Execute a SQL query using a Statement object

5) Get the results in a ResultSet object

6) Finish by closing the ResultSet , Statement and
Connection objects
交通大學資訊工程學系 蔡文能
JDBC

Java
JDBC
Application
Connection Statement
ResultSet
DataSource
交通大學資訊工程學系 蔡文能
Driver Manager
Driver Driver Driver
DataSource
DataSource
第23頁

Java JDBC
loadDriver getConnection createStatement execute(SQL) import java.sql.*; public class jdbctest { public static void main(String args[]){ try{
Class.forName("org.postgresql.Driver");
Connection con = DriverManager.getConnection
("jdbc:postgresql://lsir-cis-pc8:5401/pcmdb", "user", "passwd");
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery
yes
Result handling
More results ?
no closeStatment
("select name, number from pcmtable where number < 2"); while(rs.next())
System.out.println(rs.getString(1) + " (" + rs.getInt(2) + ")"); stmt.close() con.close();
} catch(Exception e) {
System.err.println(e);
}}} closeConnection
交通大學資訊工程學系 蔡文能 第24頁

Java JDBC
Provides static,
“ factory
” methods for creating objects implementing the connection interface.

Factory methods create objects on demand when a connection is needed to a DB driver,
DriverManager does it using its factory methods. E.g.:
Connection foo = DriverManager.getConnection(DBURL); java.sql.Connection
interface corresponds to a session (a connection with a specific database).
交通大學資訊工程學系 蔡文能 第25頁

Java JDBC
1)
2)
JDBC-ODBC Bridge.
A native API partly Java Technology enabled driver.
3)
A net protocol driver (through Middleware).
4)
JDBC
A fully Java Technology enabled driver direct built into
DB engine.
Type I
“Bridge”
Type II
“Native”
Type III
“Middleware”
ODBC
CLI (.lib)
ODBC
Driver
Middleware
Server
Type IV
“Pure”
交通大學資訊工程學系 蔡文能 第26頁

Java
Use bridging technology
Requires installation/configuration on client machines
Not good for Web / Applet e.g. ODBC Bridge
 sun.jdbc.odbc.JdbcOdbcDriver
JDBC
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第27頁

Java
Native API drivers
Requires installation/configuration on client machines
Used to leverage existing CLI libraries
Usually not thread-safe
Mostly obsolete now e.g. Intersolv Oracle Driver, WebLogic drivers
JDBC
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第28頁

Java JDBC
Calls middleware server, usually on database host
Very flexible -- allows access to multiple databases using one driver
Only need to download one driver
But it’s another server application to install and maintain e.g. Symantec DBAnywhere
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第29頁

Java
100% Pure Java -- the Holy Grail
Use Java networking libraries to talk directly to database engines
Only disadvantage: need to download a new driver for each database engine e.g. Oracle, mSQL
JDBC
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第30頁

Java
JDBC
http://industry.java.sun.com/products/jdbc/drivers http://developers.sun.com/product/jdbc/drivers/
交通大學資訊工程學系 蔡文能 第31頁

Java JDBC
交通大學資訊工程學系 蔡文能 第32頁

Java JDBC
Loading a driver

Class.forName(
“ sun.jdbc.odbc.JdbcOdbcDriver
”
);

OR
DriverManager.registerDriver(new sun.jdbc.odbc.JdbcOdbcDriver
( ) );
Making a Connection
String url = “ jdbc:oracle:oci8:@mydb ” ;
Connection con = DriverManager .getConnection(url,
“ mylogin
”
,
“ password
”
); url identifies the Data Source in Database.
See next Slide.
交通大學資訊工程學系 蔡文能 第33頁

Java JDBC
Setting system property: jdbc.drivers

A colon-separated list of driver classnames.
Can be set when starting the application java -Djdbc.drivers=org.postgresql.Driver application
Can also be set from within the Java application
Properties prp = System.getProperties(); prp.put("jdbc.drivers"
"com.mimer.jdbc.Driver:org.postgresql.Driver");
System.setProperties(prp);
The DriverManager class attempts to load all the classes specified in jdbc.drivers when the DriverManager class is initialized.
交通大學資訊工程學系 蔡文能 第34頁

Java
JDBC
Format: jdbc:subprotocol:source each driver has its own subprotocol each subprotocol has its own syntax for the source jdbc:odbc: DataSource
 e.g. jdbc:odbc:NCTUDB jdbc:msql:// host[:port]/database
 e.g. jdbc:msql://foo.nctu.edu.tw:3388/sampledb
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第35頁

Java
JDBC jdbc
The comms protocol
The machine holding the database.
The port used for the connection.
The path to the database on the machine e.g. jdbc:odbc:nctuDB
交通大學資訊工程學系 蔡文能 第36頁

Java JDBC
url identifies the Data Source in Database.
See previous Slide.
// register the driver with DriverManager
Class.forName("COM.ibm.db2.jdbc.app.DB2Driver");
String url = "jdbc:db2:DATABASE_NAME";
Connection con =DriverManager.getConnection(url,
"USERNAME", "PASSWORD");
交通大學資訊工程學系 蔡文能 第37頁

Java
A JDBC statement object is used to send your
SQL statement to the database server
A JDBC statement is associated with an open connection and not any single SQL statement
JDBC provides three classes of SQL statement

Statement

PreparedStatement

CallableStatement
JDBC
交通大學資訊工程學系 蔡文能 第38頁

Java
JDBC
Import necessary packages; Ex: import java.sql.*;
Load JDBC driver(driver should have been installed)
Data source and its location should have been registered.
Allocate Connection object, Statement object and
ResultSet object
Execute query using Statement object
Retrieve data from ResultSet object
Close Connection object.
交通大學資訊工程學系 蔡文能 第39頁

Java
Usually provided (free) by DataBase vendors
Common ones
 oracle.jdbc.driver.OracleDriver
 com.mysql.jdbc.Driver
 sun.jdbc.odbc.JdbcOdbcDriver
Need to download and install

In a webapp, put the Jar file in WEB-INF/lib
JDBC
交通大學資訊工程學系 蔡文能 第40頁

Java
JDBC
Via a DriverManager (old)
 Class.forName(DriverClassName).newInstance();
 Connection con =
DriverManager.getConnection(URL,Username,Password);
Via a DataSource (new)

Create DataSource object in configuration (e.g. in
Tomcat’s context.xml file)
交通大學資訊工程學系 蔡文能 第41頁

Java
JDBC
// con is a Connection to a DB
Statement stmt = con.createStatement();
String createINTROCS =
“
Create table INTROCS
“
+
“
(SSN Integer not null, Name VARCHAR(32),
“
+
“
Marks
Integer)
”
; stmt.executeUpdate(createINTROCS);
String insertMYCS =
“
Insert into INTROCS values
“
+
“
(123456789, abc, 100)
”
; stmt.executeUpdate(insertMYCS);
交通大學資訊工程學系 蔡文能 第42頁

Java JDBC
A ResultSet is returned when you execute an SQL statement:
// stmt is a Statement created via creatStatement( )
ResultSet rs = stmt.executeQuery("SELECT * FROM password");
A ResultSet object is similar to a ‘table’ of answers, which can be examined by moving a ‘pointer’ (cursor).
ResultSet can be used to store the query result
交通大學資訊工程學系 蔡文能 第43頁

JDBC Java
ResultSet can be used to store the query result
The ResultSet class contains many methods for accessing the value of a column of the current row
 can use the column name or position
 e.g. get the value in the lastName column: rs.getString("lastName")
The ‘tricky’ aspect is that the values are SQL data, and so must be converted to Java types/objects.
There are many methods for accessing/converting the data, e.g.
 getString(), getDate(), getInt(), getFloat(), getObject()
交通大學資訊工程學系 蔡文能 第44頁

Java JDBC
Example: SQL in Java:

Java uses int, char[..], objects , etc

SQL uses tables
Impedance mismatch = incompatible types
Why not use only one language?

SQL cannot do everything that the host language can do
Solution: use cursors
交通大學資訊工程學系 蔡文能 第45頁

Java cursor
23
5
17
John
Mark
Paul
Cursor operations: 98
Peter
 first() , last() , next() , previous() , etc.
JDBC
Typical code:
String queryINTROCS = “ select * from INTROCS ” ;
ResultSet rs = Stmt.executeQuery(queryINTROCS);
While (rs.next( )) { int ssn = rs.getInt(
“
SSN
”
);
String name = rs.getString( “ NAME ” ); int marks = rs.getInt( “ MARKS ” );
}
交通大學資訊工程學系 蔡文能
Note: column number can also be used in place of column name.
Refer to java.sql.ResulSet
API for more details
第46頁

Java
JDBC
Cursors can also modify a relation rset.updateString("script", "ebay"); rset.updateRow( ); // updates the row in the data source
The cursor can be a scrolling one: can go forward, backward first(), last(), next(), previous(), absolute(5)
We can determine the order in which the cursor will get tuples by the ORDER BY clause in the
SQL query
交通大學資訊工程學系 蔡文能 第47頁

Java JDBC
In SQL, NULL means the field is empty
Not the same as 0 or "" ( 空字串 )
In JDBC, you must explicitly ask if a field is null by calling ResultSet.isNull(column_name)
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第48頁

Java
JDBC
Variables within SQL statement
Precompiled once, multiple executions
PreparedStatement for invocation
PreparedStatement stmt = con.prepareStatement (
"SELECT * FROM data WHERE date = ?"); stmt.setDate (1, j_date);
ResultSet rset = stmt.executeQuery();
交通大學資訊工程學系 蔡文能 第49頁

Java JDBC
E.g
Unlike
“
Statement,
” it is given a SQL statement when it is created.
Used when you want to execute
“
Statement
” object many times
String insert =
“
Insert into INTROCS (?,?,?)
”
;
PreparedStatement stmt2 = con.prepareStatement(insert);
//
… stmt2.setInt(1,123456789); stmt2.setString(2, “ abc ” ); stmt2.setInt(3,100); stmt2.executeUpdate( );
交通大學資訊工程學系 蔡文能 第50頁

JDBC Java
E.g
Executing Select Statement
String query =
“
SELECT Name from INTROCS where SSN=?
”
;
PreparedStatement stmt2 = con.prepareStatement(query); stmt2.setInt(1, mySSN);
ResultSet rs = stmt2.executeQuery( );
While (rs.next( ) )
System.out.println(rs.getString(Name);
You may extract individual columns, rows or cell from the ResultSet using the metadata.
交通大學資訊工程學系 蔡文能 第51頁

Java
Used for executing stored procedures
Example
String createProcedure =
“
Create Procedure ShowGoodStudents
”
+
“ as Select
Name from INTROCS where Marks >= 90)
”
;
Stmt.executeUpdate(createProcedure);
JDBC
CallableStatement cs = con.prepareCall(
“
(call ShowGoodStudents)
”
);
ResultSet rs = cs.executeQuery( );
交通大學資訊工程學系 蔡文能 第52頁

Java
Meta data is the information about the database
Stores the number , types and properties of
ResultSet
’ s columns .
JDBC
// rs is a ResultSet
ResultSetMetaData rsm = rs.getMetaData(); int number = rsm.getColumnCount(); for (int i=0; i< number;i++)
System.out.println(rsm.getColumnName(i));
You may extract individual columns, rows or cell from the ResultSet using the metadata.
交通大學資訊工程學系 蔡文能 第53頁

Java
Meta data example
JDBC
ID Name
007
James Bond
008
Aj. Andrew
Course
Shooting
Kung Fu
Mark
99
1 meta data
交通大學資訊工程學系 蔡文能 第54頁

Java
What's the number of columns in the ResultSet?
What's a column's name ?
What's a column's SQL type?
What's the column's normal max width in chars?
What's the suggested column title for use in printouts and displays?
What's a column's number of decimal digits?
Does a column's case matter?
Is the column a cash value?
Will a write on the column definitely succeed?
Can you put a NULL in this column?
Is a column definitely not writable?
Can the column be used in a where clause?
Is the column a signed number?
Is it possible for a write on the column to succeed?
…, and so on...
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee
JDBC
第55頁

JDBC Java
// con is a Connection
DatabaseMetaData dbm = con.getMetaData();
What tables are available?
What's our user name as known to the database?
Is the database in read-only mode?
If table correlation names are supported, are they restricted to be different from the names of the tables? and so on…
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第56頁

Java
// rs is a ResultSet
ResultSetMetaData md = rs.getMetaData(); int numCols = md.
getColumnCount();
} for (int i = 0; i <= numCols; i++) { if (md.getColumnType(i) ==
Types.CHAR)
System.out.println( md.getColumnName(i) )
JDBC
交通大學資訊工程學系 蔡文能 第57頁

Java
JDBC getTableName() getPrecision()
 number of decimal digits in the column isSigned()
 returns true if column has signed numbers isCurrency() etc.
交通大學資訊工程學系 蔡文能 第58頁

Java JDBC
ResultSet rset = stmt.executeQuery(“SELECT * FROM data”);
ResultSetMetaData rsmeta = rset.getMetaData(); int numCols = rsmeta.getColumnCount(); for (int i=1; i<=numCols; i++) { int ct = rsmeta.getColumnType(i);
String cn = rsmeta.getColumnName(i);
String ctn = rsmeta.getColumnTypeName(i);
System.out.println(“Column #” + i + “: “ + cn +
“ of type “ + ctn + “ (JDBC type: “ + ct + “)”);
}
交通大學資訊工程學系 蔡文能 第59頁

Java JDBC
SQL Type
BIT
CHAR
VARCHAR
DOUBLE
FLOAT
Java class
Boolean
String
String
Double
Double
INTEGER
REAL
DATE
TIME
Integer
Double java.sql.Date
java.sql.Time
TIMESTAMP java.sql.TimeStamp
交通大學資訊工程學系 蔡文能
ResultSet get method getBoolean() getString() getString() getDouble() getDouble() getInt() getFloat() getDate() getTime() getTimestamp()
第60頁

Java
// simpJDBC.java
// Displays the firstnames and lastnames
// of the Authors table in the Books db.
import java.sql.*; public class simpJDBC { public static void main(String[] args)
{
// The URL for the Books database.
// ’Protected' by a login and password.
String url = "jdbc:odbc:Books";
String username = "anonymous";
String password = "guest";
:
交通大學資訊工程學系 蔡文能
JDBC
第61頁

Java JDBC
try {
// load the JDBC-ODBC Bridge driver
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
// connect to db using DriverManager
Connection conn =
DriverManager.getConnection( url, username, password );
// Create a statement object
Statement statement = conn.createStatement();
// Execute the SQL query
ResultSet rs = statement.executeQuery(
"SELECT lastName, firstName FROM Authors" );
:
交通大學資訊工程學系 蔡文能 第62頁

Java
}
// Print the result set while( rs.next() )
System.out.println( rs.getString("lastName") + ", " + rs.getString("firstName") );
// Close down statement.close(); conn.close();
:
JDBC
交通大學資訊工程學系 蔡文能 第63頁

Java
catch ( ClassNotFoundException cnfex ) {
System.err.println(
"Failed to load JDBC/ODBC driver." ); cnfex.printStackTrace();
System.exit( 1 ); // terminate program
} catch ( SQLException sqlex ) {
System.err.println( sqlex ); sqlex.printStackTrace();
}
} // end of main()
} // end of simpJDBC class
交通大學資訊工程學系 蔡文能
JDBC
第64頁

Java
JDBC
交通大學資訊工程學系 蔡文能 第65頁

Java JDBC
Transaction = more than one statement which must all succeed (or all fail) together
If one fails, the system must reverse all previous actions
Also can’t leave DB in inconsistent state halfway through a transaction
COMMIT = complete transaction
ROLLBACK = abort
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第66頁

Java
JDBC
JDBC allows SQL statements to be grouped together into a single transaction
Transaction control is performed by the Connection object, default mode is auto-commit, I.e., each sql statement is treated as a transaction
We can turn off the auto-commit mode with con.setAutoCommit(false);
And turn it back on with con.setAutoCommit(true);
Once auto-commit is off, no SQL statement will be committed until an explicit is invoked con.commit( );
At this point all changes done by the SQL statements will be made permanent in the database.
交通大學資訊工程學系 蔡文能 第67頁

Java
JDBC
If we don
’ t want certain changes to be made permanent, we can issue con.rollback();
Any changes made since the last commit will be ignored
– usually rollback is used in combination with Java ’ s exception handling ability to recover from unpredictable errors.
Example: // con is a Connection con.setAutocommit(false);
Statement stmt = con.createStatement( ); stmt.executeUpdate(
“
INSERT INTO INTROCS VALUES
(1234,
’
John
’
,0)
”
); con.rollback( ); stmt.executeUpdate(
“
INSERT INTO INTROCS VALUES
(1234,
’
John
’
,0)
”
); con.commit( ); con.setAutoCommit(true);
交通大學資訊工程學系 蔡文能 第68頁

Java
Each SQL statement can generate errors

Thus each SQL method should be put into a try-block
Exceptions are reported through exceptions of class SQLException
JDBC
交通大學資訊工程學系 蔡文能 第69頁

Java JDBC
Programs should recover and leave the database in a consistent state.
In Java statements which are expected to
“ throw
” an exception or a warning are enclosed in a try block.
If a statement in the try block throws an exception or warning, it can be caught in one of the corresponding catch statements
Example: // stmt is a statement try{ stmt.executeUpdate(queryINTROCS);
} catch (SQLException e){
System.out.println(e.getMessage( ))
}
交通大學資訊工程學系 蔡文能 第70頁

Java JDBC
import java.sql.*; import oracle.jdbc.driver.*; import oracle.sql.*; import java.math.BigDecimal; import java.util.Map; import java.io.*; class employee { public static void main (String args []) throws SQLException, IOException {
String user, pass, snum, namer; int enumber; user = readEntry("userid : "); pass = readEntry("password: ");
// Connect
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver ());
OracleConnection conn = (OracleConnection)
DriverManager.getConnection("jdbc:oracle:oci8:@ccdb", user,pass);
交通大學資訊工程學系 蔡文能 第71頁

Java
JDBC
Statement stmt = conn.createStatement ();
ResultSet rset = stmt.executeQuery
("select distinct eno,ename,zip,hdate from employees"); while (rset.next ()) { namer = rset.getString(2); if ( !rset.wasNull() ) {
System.out.println(rset.getInt(1) + " " + namer + " " + rset.getInt(3) + " " + rset.getDate(4));
}
}
}
System.out.println(); conn.close();
交通大學資訊工程學系 蔡文能 第72頁

Java
JDBC
//readEntry function -- to read input string static String readEntry(String prompt) { try {
StringBuffer buffer = new StringBuffer();
System.out.print(prompt);
System.out.flush(); int c = System.in.read(); while(c != '\n' && c != -1) { buffer.append((char)c); c = System.in.read();
} return buffer.toString().trim();
} catch (IOException e) { return "";
}
}
}
交通大學資訊工程學系 蔡文能 第73頁

Java
JDBC boolean next()
 activates the next row
 the first call to next() activates the first row
 returns false if there are no more rows void close()
 disposes of the ResultSet
 allows you to re-use the Statement that created it
 automatically called by most Statement methods
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第74頁

Java
JDBC
Type get Type (int columnIndex)
 returns the given field as the given type
 fields indexed starting at 1 (not 0)
Type get Type (String columnName)
 same, but uses name of field
 less efficient int findColumn(String columnName)
 looks up column index given column name
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第75頁

Java
JDBC
String getString(int columnIndex) boolean getBoolean(int columnIndex) byte getByte(int columnIndex) short getShort(int columnIndex) int getInt(int columnIndex) long getLong(int columnIndex) float getFloat(int columnIndex) double getDouble(int columnIndex)
Date getDate(int columnIndex)
Time getTime(int columnIndex)
Timestamp getTimestamp(int columnIndex)
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第76頁

Java
JDBC
String getString(String columnName) boolean getBoolean(String columnName) byte getByte(String columnName) short getShort(String columnName) int getInt(String columnName) long getLong(String columnName) float getFloat(String columnName) double getDouble(String columnName)
Date getDate(String columnName)
Time getTime(String columnName)
Timestamp getTimestamp(String columnName)
交通大學資訊工程學系 蔡文能 Copyright © 1997 Alex Chaffee 第77頁

Java
http://java.sun.com/products/jdbc/ http://developer.java.sun.com/developer/onlineTraining/
Database/JDBC20Intro/
JDBC
交通大學資訊工程學系 蔡文能 第78頁

Java JDBC
交通大學資訊工程學系 蔡文能 第79頁

Java
CORBA

Common Object Request Broker Architecture
 http://www.corba.org/
 http://www.omg.org/

J2EE Tutorial: http://java.sun.com/j2ee/1.4/docs/tutorial/doc/
JDBC
交通大學資訊工程學系 蔡文能 第80頁

Java JDBC
Defines a family of open software interface specifications for distributed object computing .
http://www.omg.org
Inside every Java Runtime Environment.
Commonly used in middle tier and backend (e.g. database) connections.
Open Source and Commercial Implementations Available
Usually buried deep inside the software

Difficult or impossible to tell when it is being used
交通大學資訊工程學系 蔡文能 第81頁

Java JDBC
Extends the benefits of object-oriented technology across process and machine boundaries to encompass entire networks.
Attempts to make remote objects appear to programmers as if they were local objects in the same process. This is called location transparency .
交通大學資訊工程學系 蔡文能 第82頁

Java JDBC
Open Standard for Distributed Object Oriented
Design
Independent of Hardware Platform
Independent of Operating System
Independent of Programming Language
Independent of Object Location http://www.omg.org
OMG = Object Management Group
Consortium of 800+ companies founded in 1989.
交通大學資訊工程學系 蔡文能 第83頁

Java JDBC
ORBs mediate between objects and things that use them
(clients)
IDL
Client Object
Object Request Broker
IDL
IDL = Interface Definition Language
交通大學資訊工程學系 蔡文能 第84頁

Java JDBC
The glue that binds parts together is the ORB
The Interface to an object can be distributed over a network
Shape of boundary is defined in IDL
IDL = Interface Definition Language
交通大學資訊工程學系 蔡文能 第85頁

Java
C
C++ Perl Delphi Ada Java
JDBC
ORB ORB
CORBA / IIOP—Internet Inter-ORB Protocol
ORB
Application
ActiveX
交通大學資訊工程學系 蔡文能 第86頁

Java JDBC

The Internet Inter-ORB Protocol , defined in the Spec as a vendor-independent, wire-level network protocol on top of TCP/IP. This allows
ORB implementations of different vendors to interoperate.
交通大學資訊工程學系 蔡文能 第87頁

Java
JDBC
謝謝捧場 http://www.csie.nctu.edu.tw/~tsaiwn/java/
蔡文能
交通大學資訊工程學系 蔡文能 第88頁