JDBC操作数据库的增加、删除、更新、查找实例分析

package cn.com.JDBC;import java.sql.Connection;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;public class CRUD { public static void main(String[] args) throws SQLException {  // TODO Auto-generated method stub  //create();  //update();  delete();  read(); } static void delete() throws SQLException {  Connection conn=null;  Statement st=null;  ResultSet resultset=null;  try {   //2.建立连接   conn=JdbcUtils.getConnection();   //单例设计模式   conn=JdbcUtilsSingle.getInstance().getConnection();   //3.创建语句   st=conn.createStatement();   //4.执行语句   String sql="delete from user where id>5";   int i=st.executeUpdate(sql);   System.out.println("i="+i);  } finally  {   JdbcUtils.free(resultset, st, conn);  } } static void update() throws SQLException {  Connection conn=null;  Statement st=null;  ResultSet resultset=null;  try {   //2.建立连接   conn=JdbcUtils.getConnection();   //单例设计模式   conn=JdbcUtilsSingle.getInstance().getConnection();   //3.创建语句   st=conn.createStatement();   //4.执行语句   String sql="update user set money=money+20";   int i=st.executeUpdate(sql);   System.out.println("i="+i);  } finally  {   JdbcUtils.free(resultset, st, conn);  } } static void create() throws SQLException {  Connection conn=null;  Statement st=null;  ResultSet resultset=null;  try {   //2.建立连接   conn=JdbcUtils.getConnection();   //单例设计模式   conn=JdbcUtilsSingle.getInstance().getConnection();   //3.创建语句   st=conn.createStatement();   //4.执行语句   String sql="insert into user(name,birthday,money) values('wy','2011-09-23','2894656')";   int i=st.executeUpdate(sql);   System.out.println("i="+i);  } finally  {   JdbcUtils.free(resultset, st, conn);  } } static void read() throws SQLException {  Connection conn=null;  Statement st=null;  ResultSet resultset=null;  try {   //2.建立连接   conn=JdbcUtils.getConnection();   //单例设计模式   conn=JdbcUtilsSingle.getInstance().getConnection();   //3.创建语句   st=conn.createStatement();   //4.执行语句   resultset=st.executeQuery("select id,name,birthday,money from user");   //5.处理结果   while(resultset.next())   {    System.out.println(resultset.getObject("id"));    System.out.println(resultset.getObject("name"));    System.out.println(resultset.getObject("birthday"));    System.out.println(resultset.getObject("money"));   }  } finally  {   JdbcUtils.free(resultset, st, conn);  } }}package cn.com.JDBC;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;public class JdbcUtils { private static String url="jdbc:mysql://localhost:3306/jdbc"; private static String user="root"; private static String password="123"; private JdbcUtils() { } static {  try  {   Class.forName("com.mysql.jdbc.Driver");  }  catch(ClassNotFoundException e)  {   throw new ExceptionInInitializerError(e);  } } public static Connection getConnection() throws SQLException {  return DriverManager.getConnection(url, user, password); } public static void free(ResultSet resultset,Statement st,Connection conn) {  //6.释放资源  try{  if(resultset!=null)   resultset.close();  } catch (SQLException e) {   // TODO Auto-generated catch block   e.printStackTrace();  }  finally  {   try   {    if(st!=null)     st.close();   } catch (SQLException e) {    // TODO Auto-generated catch block    e.printStackTrace();   }   finally   {    if(conn!=null)     try {      conn.close();     } catch (SQLException e) {      // TODO Auto-generated catch block      e.printStackTrace();     }   }  } }}