JDBC. Prepared by Viska Mutiawani. 1

Transcription

1 JDBC Prepared by Viska Mutiawani 1 viska@unsyiah.ac.id

2 Subtopik JDBC Pengenalan JDBC JDBC driver Package java.sql Cara menggunakan JDBC Advance 2 viska@unsyiah.ac.id

3 Pengenalan JDBC 3 viska@unsyiah.ac.id

4 JDBC Java Database Connectivity JDBC is a standard interface for connecting to relational databases from Java. The JDBC classes and interfaces are in the java.sql package. JDBC 1.22 is part of JDK 1.1; JDBC 2.0 is part of Java 2 4 viska@unsyiah.ac.id

5 Apakah itu JDBC? JDBC provides Java applications with access to most database systems via SQL The architecture and API closely resemble Microsoft's ODBC JDBC 1.0 was originally introduced into Java 1.1 JDBC 2.0 was added to Java 1.2 JDBC is based on SQL-92 JDBC classes are contained within the java.sql package There are few classes There are several interfaces 5 viska@unsyiah.ac.id

6 Database connectivity history Before APIs like JDBC and ODBC, database connectivity was tedious Each database vendor provided a function library for accessing their database The connectivity library was proprietary. If the database vendor changed for the application, the data access portions had to be rewritten If the application was poorly structured, rewriting its data access might involve rewriting the majority of the application The costs incurred generally meant that application developers were stuck with a particular database product for a given application 6 viska@unsyiah.ac.id

7 Arsitektur JDBC With JDBC, the application programmer uses the JDBC API The developer never uses any proprietary APIs Any proprietary APIs are implemented by a JDBC driver There are 4 types of JDBC Drivers Java Application JDBC API JDBC DriverManager JDBC Driver JDBC Driver 7 viska@unsyiah.ac.id

8 8 JDBC Drivers

9 JDBC Drivers There are 4 types of JDBC Drivers: Type 1 - JDBC-ODBC Bridge Type 2 - JDBC-Native Bridge Type 3 - JDBC-Net Bridge Type 4 - Direct JDBC Driver Type 1 only runs on platforms where ODBC is available ODBC must be configured separately Type 2 Drivers map between a proprietary Database API and the JDBC API Type 3 Drivers are used with middleware products Type 4 Drivers are written in Java In most cases, type 4 drivers are preferred 9 viska@unsyiah.ac.id

10 JDBC Driver Types 10

11 Type 1: JDBC-ODBC Bridge Driver This is an approach wherein the implemented class in Java makes calls to the code written in Microsoft languages (native), which speaks directly to the database. The first category of JDBC drivers provides a bridge between the JDBC and the ODBC API. The bridge translates the standard JDBC calls and sends them to the ODBC data source via ODBC libraries. Type 1 drivers use a bridge technology to connect a Java client to an ODBC database system. The JDBC-ODBC Bridge from Sun and InterSolv is the only extant example of a Type 1 driver. Type 1 drivers require some sort of non-java software to be installed on the machine running your code, and they are implemented using native code. 11 viska@unsyiah.ac.id

12 Type 2: JDBC-Native API In a Type 2 driver, JDBC API calls are converted into native C/C++ API calls which are unique to the database. These drivers typically provided by the database vendors and used in the same manner as the JDBC-ODBC Bridge, the vendor-specific driver must be installed on each client machine. This is an approach wherein the implemented class in Java makes calls to the code written from the database provider (native), which speaks directly to the database. If we change the Database we have to change the native API as it is specific to a database and they are mostly obsolete now but you may realize some speed increase with a Type 2 driver, because it eliminates ODBC's overhead. The Oracle Call Interface (OCI) driver is an example of a Type 2 driver. 12 viska@unsyiah.ac.id

13 Type 3: JDBC-Net pure Java In a Type 3 driver, a three-tier approach is used to accessing databases. The JDBC clients use standard network sockets to communicate with an middleware application server. The socket information is then translated by the middleware application server into the call format required by the DBMS, and forwarded to the database server. You can think of the application server as a JDBC "proxy," meaning that it makes calls for the client application. As a result, you need some knowledge of the application server's configuration in order to effectively use this driver type. The Java client application sends a JDBC calls through a JDBC driver to the intermediate data access server,which completes the request to the data source using another driver. This driver uses a database independent protocol, to communicate database request to a server component which then translate the request into a DB specific protocol. 13 viska@unsyiah.ac.id

14 Type 4: 100% pure Java In a Type 4 driver, a pure Java-based driver that communicates directly with vendor's database through socket connection. This is the highest performance driver available for the database and is usually provided by the vendor itself. This kind of driver is extremely flexible, you don't need to install special software on the client or server. Further, these drivers can be downloaded dynamically. This is an approach wherein the implemented class in Java (implemented by the database provider) speaks directly to the database. In other words, it is a pure Java library that translates JDBC request directly to a Database specific protocol. MySQL's Connector/J driver is a Type 4 driver. Because of the proprietary nature of their network protocols, database vendors usually supply type 4 drivers. 14 viska@unsyiah.ac.id

15 So which driver? If you are accessing one type of database, such as Oracle, Sybase, or IBM, the preferred driver type is 4. If your Java application is accessing multiple types of databases at the same time, type 3 is the preferred driver. Type 2 drivers are useful in situations where a type 3 or type 4 driver is not available yet for your database. The type 1 driver is not considered a deploymentlevel driver and is typically used for development and testing purposes only. 15 viska@unsyiah.ac.id

16 16 Package java.sql

17 JDBC Components 17

18 JDBC Classes DriverManager Types Date Time Manages JDBC Drivers Used to Obtain a connection to a Database Defines constants which identify SQL types Used to Map between java.util.date and the SQL DATE type Used to Map between java.util.date and the SQL TIME type TimeStamp Used to Map between java.util.date and the SQL TIMESTAMP type 18 viska@unsyiah.ac.id

19 JDBC Interfaces Driver All JDBC Drivers must implement the Driver interface. Used to obtain a connection to a specific database type Connection Represents a connection to a specific database Used for creating statements Used for managing database transactions Used for accessing stored procedures Used for creating callable statements Statement Used for executing SQL statements against the database 19 viska@unsyiah.ac.id

20 JDBC Interfaces ResultSet Represents the result of an SQL statement Provides methods for navigating through the resulting data PreparedStatement Similar to a stored procedure An SQL statement (which can contain parameters) is compiled and stored in the database CallableStatement Used for executing stored procedures DatabaseMetaData Provides access to a database's system catalogue ResultSetMetaData Provides information about the data contained within a ResultSet 20 viska@unsyiah.ac.id

21 Cara Menggunakan JDBC 21

22 Using JDBC To execute a statement against a database, the following flow is observed Load the driver (Only performed once) Obtain a Connection to the database (Save for later use) Obtain a Statement object from the Connection Use the Statement object to execute SQL. Updates, inserts and deletes return Boolean. Selects return a ResultSet Navigate ResultSet, using data as required Close ResultSet Close Statement Do NOT close the connection The same connection object can be used to create further statements A Connection may only have one active Statement at a time. Do not forget to close the statement when it is no longer needed. Close the connection when you no longer need to access the database 22 viska@unsyiah.ac.id

23 Overview of Querying a Database With JDBC Connect Query Process results Close 23 viska@unsyiah.ac.id

24 Stage 1: Connect Connect Register the driver Query Connect to the database Process results Close 24

25 A JDBC Driver Is an interpreter that translates JDBC method calls to vendor-specific database commands JDBC calls Driver Database commands Database Implements interfaces in java.sql Can also provide a vendor s extensions to the JDBC standard 25 viska@unsyiah.ac.id

26 About JDBC URLs JDBC uses a URL to identify the database connection. jdbc:<subprotocol>:<subname> Protocol Subprotocol Database identifier jdbc:oracle:<driver>:@<database> 26 viska@unsyiah.ac.id

27 Nama URL database: JDBC-ODBC : jdbc:odbc:nama_database Oracle : jdbc:oracle:thin:@nama_host:1521:namadb MySQL: jdbc:mysql://nama_host:3306/namadb PostgreSQL: jdbc:postgresql://nama_host:5432/namadb Microsoft SQLServer 2000 : jdbc:microsoft:sqlserver://nama_host:1433;databasename=n amadb 27 viska@unsyiah.ac.id

28 JDBC URLs with Oracle Drivers Thin driver OCI driver entry> Server-side driver: Use the default connection 28

29 How to Make the Connection 1. Register the driver. Class.forName("com.mysql.jdbc.Driver"); 2. Connect to the database. Connection conn = DriverManager.getConnection (URL, userid, password); Connection conn = DriverManager.getConnection(" ("jdbc:mysql://loc alhost/books", "root", "mysql"); 29 viska@unsyiah.ac.id

30 Using Connection java.sql.connection createstatement() preparestatement(string) preparecall(string) commit() rollback() getmetadata() close() isclosed() Creating Statement Transaction Management Get database metadata Connection related 30

31 Stage 2: Query Connect Query Create a statement Process results Query the database Close 31 viska@unsyiah.ac.id

32 The Statement Object A Statement object sends your SQL statement to the database. You need an active connection to create a JDBC statement. Statement has three methods to execute a SQL statement: executequery() for QUERY statements executeupdate() for INSERT, UPDATE, DELETE, or DDL statements execute() for either type of statement 32 viska@unsyiah.ac.id

33 How to Query the Database 1. Create an empty statement object. Statement stmt = conn.createstatement(); 2. Execute the statement. ResultSet rset = stmt.executequery(statement); int count = stmt.executeupdate(statement); boolean isquery = stmt.execute(statement); 33 viska@unsyiah.ac.id

34 Querying the Database: Examples Execute a select statement. Statement stmt = conn.createstatement(); ResultSet rset = stmt.executequery ("select RENTAL_ID, STATUS from ACME_RENTALS"); Execute a delete statement. Statement stmt = conn.createstatement(); int rowcount = stmt.executeupdate ("delete from ACME_RENTAL_ITEMS where rental_id = 1011"); 34 viska@unsyiah.ac.id

35 Stage 3: Process the Results Connect Query Step through the results Process results Assign results to Java variables Close 35

36 The ResultSet Object JDBC returns the results of a query in a ResultSet object. A ResultSet maintains a cursor pointing to its current row of data. Use next() to step through the result set row by row. getstring(), getint(), and so on assign each value to a Java variable. 36 viska@unsyiah.ac.id

37 How to Process the Results 1. Step through the result set. while (rset.next()) { } 2. Use getxxx() to get each column value. String val = rset.getstring(colname); String val = rset.getstring(colindex); while (rset.next()) { String title = rset.getstring("title"); String year = rset.getstring("year"); // Process or display the data } 37 viska@unsyiah.ac.id

38 How to Handle SQL Null Values Java primitive types cannot have null values. Do not use a primitive type when your query might return a SQL null. Use ResultSet.wasNull() to determine whether a column has a null value. while (rset.next()) { String year = rset.getstring("year"); if (rset.wasnull() { // Handle null value } } 38 viska@unsyiah.ac.id

39 Mapping Database Types to Java Types ResultSet maps database types to Java types. ResultSet rset = stmt.executequery ("select RENTAL_ID, RENTAL_DATE, STATUS from ACME_RENTALS"); int id = rset.getint(1); Date rentaldate = rset.getdate(2); String status = rset.getstring(3); Col Name RENTAL_ID RENTAL_DATE Type NUMBER DATE 39 STATUS viska@unsyiah.ac.id VARCHAR2

40 SQL Types/Java Types Mapping SQL Type Java Type CHAR String VARCHAR String LONGVARCHAR String NUMERIC java.math.bigdecimal DECIMAL java.math.bigdecimal BIT boolean TINYINT int SMALLINT int INTEGER int BIGINT long REAL float FLOAT double DOUBLE double BINARY byte[] VARBINARY byte[] DATE java.sql.date TIME java.sql.time 40 TIMESTAMP java.sql.timestamp

41 Stage 4: Close Connect Query Close the result set Process results Close the statement Close Close the connection 41

42 How to Close the Connection 1. Close the ResultSet object. rset.close(); 2. Close the Statement object. stmt.close(); 3. Close the connection (not necessary for server-side driver). conn.close(); 42

43 Example Code: Connection aconnection; try { Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); } catch(classnotfoundexception x) { System.out.println("Cannot find driver class. Check CLASSPATH"); return; } try { aconnection = DriverManager.getConnection("jdbc:odbc:MyDatabase", "Username", "Password"); } catch(sqlexception x) { System.out.println("Exception connecting to database:" + x); return; } 43 viska@unsyiah.ac.id

44 Example Code (continued): try { Statement astmt = aconnection.createstatement(); StringBuffer sb = new StringBuffer("SELECT Employee_id, Employee_Name"); sb.append(" FROM Employee WHERE EmployeeId>100"); ResultSet rs = astmt.executequery(sb.tostring()); while(rs.next()) { int employeeid = rs.getint(1); String employeename = rs.getstring(2); } System.out.println("Id:" + employeeid + "\nname:" + employeename); rs.close(); astmt.close(); } catch(sqlexception x) { System.out.println("Exception while executing query:" + x); } 44 viska@unsyiah.ac.id

45 More Advanced Dynamic Query using MetaData 45

46 The DatabaseMetaData Object The Connection object can be used to get a DatabaseMetaData object. This object provides more than 100 methods to obtain information about the database. 46 viska@unsyiah.ac.id

47 How to Obtain Database Metadata 1. Get the DatabaseMetaData object. DatabaseMetaData dbmd = conn.getmetadata(); 2. Use the object s methods to get the metadata. DatabaseMetaData dbmd = conn.getmetadata(); String s1 = dbmd geturl(); String s2 = dbmd.getsqlkeywords(); boolean b1 = dbmd.supportstransactions(); boolean b2 = dbmd.supportsselectforupdate(); 47 viska@unsyiah.ac.id

48 The ResultSetMetaData Object The ResultSet object can be used to get a ResultSetMetaData object. ResultSetMetaData object provides metadata, including: Number of columns in the result set Column type Column name 48 viska@unsyiah.ac.id

49 How to Obtain Result Set Metadata 1. Get the ResultSetMetaData object. ResultSetMetaData rsmd = rset.getmetadata(); 2. Use the object s methods to get the metadata. ResultSetMetaData rsmd = rset.getmetadata(); for (int i = 0; i < rsmd.getcolumncount(); i++) { String colname = rsmd.getcolumnname(i); int coltype = rsmd.getcolumntype(i); } 49 viska@unsyiah.ac.id

50 The PreparedStatement Object A PreparedStatement object holds precompiled SQL statements. Use this object for statements you want to execute more than once. A prepared statement can contain variables that you supply each time you execute the statement. 50 viska@unsyiah.ac.id

51 How to Create a Prepared Statement 1.Register the driver and create the database connection. 2.Create the prepared statement, identifying variables with a question mark (?). PreparedStatement pstmt = conn.preparestatement("update ACME_RENTALS set STATUS =? where RENTAL_ID =?"); PreparedStatement pstmt = conn.preparestatement("select STATUS from ACME_RENTALS where RENTAL_ID =?"); 51 viska@unsyiah.ac.id

52 How to Execute a Prepared Statement 1. Supply values for the variables. pstmt.setxxx(index, value); 2. Execute the statement. pstmt.executequery(); pstmt.executeupdate(); PreparedStatement pstmt = conn.preparestatement("update ACME_RENTALS set STATUS =? where RENTAL_ID =?"); pstmt.setstring(1, "OUT"); pstmt.setint(2, rentalid); pstmt.executeupdate(); 52 viska@unsyiah.ac.id

53 The CallableStatement Object A CallableStatement object holds parameters for calling stored procedures. A callable statement can contain variables that you supply each time you execute the call. When the stored procedure returns, computed values (if any) are retrieved through the CallabableStatement object. 53 viska@unsyiah.ac.id

54 How to Create a Callable Statement Register the driver and create the database connection. Create the callable statement, identifying variables with a question mark (?). CallableStatement cstmt = conn.preparecall("{call " + ADDITEM + "(?,?,?)}"); cstmt.registeroutparameter(2,types.integer); cstmt.registeroutparameter(3,types.double); 54 viska@unsyiah.ac.id

55 How to Execute a Callable Statement 1. Set the input parameters. cstmt.setxxx(index, value); 2. Execute the statement. cstmt.execute(statement); 3. Get the output parameters. var = cstmt.getxxx(index); 55 viska@unsyiah.ac.id

56 Using Transactions The server-side driver does not support autocommit mode. With other drivers: New connections are in autocommit mode. Use conn.setautocommit(false) to turn autocommit off. To control transactions when you are not in autocommit mode: conn.commit(): Commit a transaction conn.rollback(): Roll back a transaction 56 viska@unsyiah.ac.id

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