A DBA Perspective to J2EE课件.ppt

What is a J2EE Container J2EE applications run in a special environment called a J2EE Container/Server Oracle’s container is named OracleAS Containers for J2EE (OC4J) EJB Container Client EJB Bean Home Interfaces J2EE Server Web Container Servlet/JSP J2EE Architecture Database and Legacy Systems Enterprise JavaBeans JSP PagesServlets Web BrowserApplets Application Clients Client Tier Web Tier Business Tier EIS Tier JDBC / J2CA What is JDBC Standard API for accessing relational databases from Java Issue SQL statements Call server-side procedural logic Conceptually similar to ODBC Translates JDBC method calls to vendor-specific database commands Implements interfaces defined in the java.sql and javax.sql packages Can also provide a vendor’s extensions to the JDBC standard Driver JDBC calls Database commands Database JDBC Driver Database Oracle JDBC Drivers Oracle Database Remote Database Java Engine SQL Engine PL/SQL Engine Thin Driver (Type IV) OCI Driver (Type II) Java Sockets OCI C Library KPRB C Library Server-Side Internal Driver Server-Side Thin Driver Java Sockets Thin driver: OCI driver: Server-Side internal driver: jdbc:oracle:thin:@host:port:SID jdbc:oracle:oci:@TNSNAMES entry Sample JDBC URLs for Oracle jdbc:oracle:thin:@:1521:ORCL jdbc:oracle:oci:@dbdev jdbc:oracle:kprb: DriverManager.registerDriver (new oracle.jdbc.OracleDriver()); Connection conn = DriverManager.getConnection (jdbc:oracle:thin:@myhost:1521:orcl,  scott, tiger); Connecting to the Database Register the driver Connect to the database Issue statement Close Connect Process results JNDI Data Sources Newer way to access connection information More flexible, portable than hard-coding URLs Look up connection details by logical name Typical for J2EE applications Context ctx = new InitialContext(); OracleDataSource ods = (OracleDataSource)ctx.lookup(jdbc/TestDB); Connection conn = ods.getConnection(); JNDI API JNDI Lookup JDBC Connection Database LDAP CORBA/COS