Basic operation of Java database

Java Database Basic Operations

1. Java database Operation Basic process

2, a few commonly used important skills:

Scrollable, updated recordsets

Batch Update

Transaction processing

Java database Operation basic process: Get database connection-Execute SQL statement-Process Execution result-release database connection

1. Get the database connection

1) using 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)

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 used in JSP

2. Execute SQL statement

1 using statement to execute SQL statements

String sql;
　Statement sm = cn.createStatement();
　sm.executeQuery(sql);// 执行数据查询语句（select）
　sm.executeUpdate(sql);// 执行数据更新语句（delete、update、insert、drop等）statement.close();

2 using PreparedStatement to execute SQL statements

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();// 查询
　int c = ps.executeUpdate();// 更新

3, processing the results of implementation

Query statement that returns a recordset resultset

UPDATE statement, returning a number that represents the number of records affected by the update

The method of ResultSet

1, Next (), move the cursor back one row, or False if successful return true;

2, GETINT ("id") or getsting ("name"), returns the value of a field under the current cursor

4, Release the connection

Cn.close ();

Generally, close the resultset first, then close the statement (or PreparedStatement), and finally close the connection