JDBC (Java Database Connectivity)

Transcription

1 JDBC (Java Database Coectivity) Database System Cocepts, 6 th Ed. Siberschatz, Korth ad Sudarsha See for coditios o re-use

2 JDBC Java API for commuicatig with database systems supportig SQL Supports a variety of features for queryig ad updatig data, ad for retrievig query resuts Aso supports metadata retrieva, such as queryig about reatios preset i the database ad the ames ad types of reatio attributes What does JDBC do? Estabish a coectio with a database Sed SQL statemets Process the resuts JAVA Appicatio JDBC Ca JDBC Driver Database Commad Database Database System Cocepts - 6 th Editio 5.2 Siberschatz, Korth ad Sudarsha

3 JDBC Programmig Steps Coect 1) Register the driver 2) Create a coectio to the database Query 1) Create a statemet 2) Query the database Process Resuts 1) Get a resut set 2) Assig resuts to Java variabes Cose 1) Cose the resut set 2) Cose the statemet 3) Cose the coectio Database System Cocepts - 6 th Editio 5.3 Siberschatz, Korth ad Sudarsha

4 Skeeto Code import java.sq.*; Cass.forName(DRIVERNAME); Loadig a JDBC driver Coectio co = DriverMaager.getCoectio( CONNECTIONURL, DBID, DBPASSWORD); Coectig to a database Statemet stmt = co.createstatemet(); ResutSet rs = stmt.executequery( SELECT a, b, c FROM member); Whie(rs.ext()) { It x = rs.getit( a ); Strig s = rs.getstrig( b ); Foat f = rs.getfoat( c ); } Executig SQL Processig the resut set rs.cose(); stmt.cose(); co.cose(); Cosig the coectios Database System Cocepts - 6 th Editio 5.4 Siberschatz, Korth ad Sudarsha

5 Step 1 : Loadig a JDBC Driver A JDBC driver is eeded to coect to a database Loadig a driver requires the cass ame of the driver Tibero: com.tmax.tibero.jdbc.tbdriver 4 Add $TB_HOME/ciet/ib/jar/tibero5-jdbc.jar to Java casspath 4 Import tbjdbc package i Java fie import com.tmax.tibero.jdbc.*; import com.tmax.tibero.jdbc.ext.*; Orace: orace.jdbc.driver.oracedriver MySQL: com.mysq.jdbc.driver Loadig the driver cass Cass.forName("com.tmax.tibero.jdbc.TbDriver"); It is possibe to oad severa drivers The cass DriverMaager maages the oaded driver(s) Database System Cocepts - 6 th Editio 5.5 Siberschatz, Korth ad Sudarsha

6 Step 2 : Coectig to a Database JDBC URL for a database Idetifies the database to be coected Cosists of three-part: jdbc:<subprotoco>:<subame> Protoco: JDBC is the oy protoco i JDBC Sub-protoco: idetifies a database driver Subame: idicates the ocatio ad ame of the database to be accessed. Sytax is driver specific Creatig a Coectio object (i java.sq.*) Coectio co = DriverMaager.getCoectio("jdbc:tibero:thi:@ocahost:8629:tibero", "tibero", "tmax"); DB user id, password DriverMaager (server IP):(port):(SID) Aows you to coect to a database usig the specified JDBC driver, database ocatio, database ame, userame ad password Returs a Coectio object which ca the be used to commuicate with the database Database System Cocepts - 6 th Editio 5.6 Siberschatz, Korth ad Sudarsha

7 Step 3 : Executig SQL Statemet object (i java.sq.*) Seds SQL to the database to be executed Ca be obtaied from a Coectio object Statemet statemet = co.createstatemet(); Statemet has three methods to execute a SQL statemet: executequery() for QUERY statemets 4 Returs a ResutSet which cotais the query resuts ResutSet rset = stmt.executequery ("seect RENTAL_ID, STATUS from ACME_RENTALS"); executeupdate() for INSERT, UPDATE, DELETE, or DDL statemets 4 Returs a iteger, the umber of affected rows from the SQL it rowcout = stmt.executeupdate ("deete from ACME_RENTAL_ITEMS where reta_id =1011"); execute() for either type of statemet Database System Cocepts - 6 th Editio 5.7 Siberschatz, Korth ad Sudarsha

8 Step 4 : Processig the Resuts JDBC returs the resuts of a query i a ResutSet object (i java.sq.*) ResutSet object cotais a of the rows which satisfied the coditios i a SQL statemet A ResutSet object maitais a cursor poitig to its curret row of data Use ext() to step through the resut set row by row 4 ext() returs TRUE if there are sti remaiig records getstrig(), getit(), ad getxxx() assig each vaue to a Java variabe Exampe Statemet stmt = co.createstatemet(); ResutSet rs = stmt.executequery( SELECT ID, ame, score FROM tabe1 ); Whie (rs.ext()) { NOTE This code wi ot skip it id = rs.getit( ID ); the first record } Strig ame = rs.getstrig( ame ); foat score = rs.getfoat( score ); System.out.prit( ID= + id + + ame + + score); Database System Cocepts - 6 th Editio 5.8 Tabe1 ID ame score 1 James Smith Doad 80.2 Output ID=1 James 90.5 ID=2 Smith 45.7 ID=3 Doad 80.2 Siberschatz, Korth ad Sudarsha

9 Step 5 : Cosig Database Coectio It is a good idea to cose the Statemet ad Coectio objects whe you have fiished with them Cose the ResutSet object rs.cose(); Cose the Statemet object stmt.cose(); Cose the Coectio object co.cose(); Database System Cocepts - 6 th Editio 5.9 Siberschatz, Korth ad Sudarsha

10 The PreparedStatemet Object A PreparedStatemet object hods precompied SQL statemets Use this object for statemets you wat to execute more tha oce A PreparedStatemet ca cotai variabes (?) that you suppy each time you execute the statemet // Create the prepared statemet PreparedStatemet pstmt = co.preparestatemet( UPDATE tabe1 SET status =? WHERE id =? ) // Suppy vaues for the variabes pstmt.setstrig (1, out ); pstmt.setit(2, id); // Execute the statemet pstmt.executeupdate(); Database System Cocepts - 6 th Editio 5.10 Siberschatz, Korth ad Sudarsha

11 Trasactios Cotro i JDBC Trasactio: more tha oe statemet that must a succeed (or a fai) together If oe fais, the system must reverse a previous actios E.g., updatig severa tabes due to customer purchase COMMIT = compete trasactio ROLLBACK = cace a actios By defaut, each SQL statemet is treated as a separate trasactio that is committed automaticay i JDBC bad idea for trasactios with mutipe updates Ca tur off automatic commit o a coectio co.setautocommit(fase); Trasactios must the be committed or roed back expicity co.commit(); or co.roback(); co.setautocommit(true) turs o automatic commit Database System Cocepts - 6 th Editio 5.11 Siberschatz, Korth ad Sudarsha

12 Trasactios Cotro Exampe co.setautocommit(fase); try { PreparedStatemet pstmt = co.preparestatemet( "update BakAccout set amout = amout +? where accoutid =?"); pstmt.setit(1,-100); pstmt.setit(2, 13); pstmt.executeupdate(); pstmt.setit(1, 100); pstmt.setit(2, 72); pstmt.executeupdate(); co.commit(); catch (SQLExceptio e) { co.roback(); } Database System Cocepts - 6 th Editio 5.12 Siberschatz, Korth ad Sudarsha

13 Other JDBC Features Hadig arge object types getbob() ad getcob() that are simiar to the getstrig() method, but retur objects of type Bob ad Cob, respectivey get data from these objects by getbytes() associate a ope stream with Java Bob or Cob object to update arge objects 4 bob.setbob(it parameteridex, IputStream iputstream). Database System Cocepts - 6 th Editio 5.13 Siberschatz, Korth ad Sudarsha

14 Refereces Database System Cocepts, Ch JDBC Orace JDBC site Java JDBC Tutoria Java API for java.sq package Tibero JDBC 개발자안내서 > 기술문서 > Tibero Database System Cocepts - 6 th Editio 5.14 Siberschatz, Korth ad Sudarsha