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,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,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,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,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();
     }
   }
  }
 }
}