Java Database Basic Operations (RPM)

JAVA Basic Database Operations Guide

Basic process of Java database operation: Get database connection-Execute SQL statement-Process Execution Result-free database connection. I. Get a database connection 1. Use DriverManager to Access database connection Example: String classname,url,uid,pwd; ClassName = "Oracle.jdbc.driver.OracleDriver"; url = "JDBC:ORACLE:THIN:@127.0.0.1:1521:ORASVR; UID = "System"; PWD = "Manager"; Class.forName (ClassName); Connection cn = drivermanager.getconnection (URL,UID,PWD); 2, using Jndi (Java naming and directory services) way Example: String Jndi = "jdbc/db"; Context CTX = (context) new InitialContext (). Lookup ("java:comp/env"); DataSource ds = (DataSource) ctx.lookup (JNDI); Connection cn = Ds.getconnection (); More in JSP. Second, execute the SQL statement 1. Execute SQL statements with statement String SQL; Statement sm = cn.createstatement (); Sm.executequery (SQL); Execute Data query statement (SELECT) Sm.executeupdate (SQL); Execute Data UPDATE statement (delete, update, insert, DROP, etc.) Statement.close (); 2. Execute SQL statements with PreparedStatement String SQL; sql = "INSERT into user (Id,name) VALUES (?,?)"; PreparedStatement PS = cn.preparestatement (SQL); Ps.setint (1,XXX); Ps.setstring (2,XXX); ... ResultSet rs = Ps.executequery (); Inquire int c = Ps.executeupdate (); Update Iii. processing the results of the implementation A query statement that returns the recordset resultset. UPDATE statement, which returns a number indicating the number of records affected by the update ResultSet the method (1) Next () Moves the cursor back one line, or False if it returns true; (2) getInt ("id") or getsting ("name"), which returns the value of a field under the current cursor Iv. Release the connection Cn.close (); In general, close resultset first, then close statement (or PreparedStatement), and finally close connection. (i) A scrollable, updated set of records 1. Create scrollable, updated statement Statement sm = cn.createstatement (resultset.type_scroll_ensitive, RESULTSET.CONCUR_READ_ONLY); The resultset obtained by the statement is a scrollable 2. Specify parameters when creating PreparedStatement Preparedstatemet PS = cn.preparestatement (sql,resultset.type_scroll_insensitive, RESULTSET.CONCUR_READ_ONLY); Resultset.absolute (9000); #p # (b) Batch Update 1, Statement Statement sm = cn.createstatement (); Sm.addbatch (SQL1); Sm.addbatch (SQL2); ... Sm.executebatch () A statement object that can execute multiple SQL statements after a batch update. The multiple statements can be delete, update, INSERT, etc. or both 2, PreparedStatement PreparedStatement PS = cn.preparedstatement (SQL); { Ps.setxxx (1,XXX); ... Ps.addbatch (); } Ps.executebatch (); A PreparedStatement, you can put an SQL statement, transform parameters to execute multiple times, one update. (iii) Processing of transactions 1. Turn off automatic submission of connection Cn.setautocommit (FALSE); 2. Execute a series of SQL statements Important: Before executing each new SQL statement, the last statement (or Preparedstatemet) that executed the SQL statement must first close Statement SM; SM = cn.createstatement (insert into user ...); Sm.executeupdate (); Sm.close (); SM = cn.createstatement ("INSERT INTO corp ..."); Sm.executeupdate (); Sm.close (); 3. Submit Cn.commit (); 4, if an exception occurs, then rollback Cn.rollback ();

Java Database Basic Operations (RPM)