JDBC连接数据库

JDBC是使用Hibernate的基础，Hibernate是对JDBC复杂操作的封装,简化了大量的SQL语句编写。

JDBC链接数据库步骤:

1. 注册驱动 mysql驱动 oracle驱动

2. 获取连接
   使用DriverManager.getConnection()产生Connection

   连接数据库的url: jdbc:oracle:thin:@localhost:1521:XE
   jdbc:mysql://127.0.0.1:3306/zmysql user password

3. 创建pstmt/stmt对象
   ,如果有占位符替换占位符
4. 执行sql
   int executeUpdate();
   增 删 改Result executeQuery();
   查 execute();
5. 如果有结果集，处理结果集
6. 释放资源
   Connection
   PreparedStatement
   ResultSet
   后创建的先释放

导包：

以连接MySQL数据库为例，先将驱动包Jar包导入：

Student Pojo类:

package com.ssh.jdbc;


import java.io.Serializable;

public class Student implements Serializable {
private static final long serialVersionUID = 1L;

private Long id;
private String name;
private Integer age;

public Student() {

    }
public Student(Long id, String name, Integer age) {
super();
this.id = id;
this.name = name;
this.age = age;
    }


public Long getId() {
return id;
    }
public void setId(Long id) {
this.id = id;
    }
public String getName() {
return name;
    }
public void setName(String name) {
this.name = name;
    }
public Integer getAge() {
return age;
    }
public void setAge(Integer age) {
this.age = age;
    }
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
    }
}

ConnectionFactory:

对于Connection的创建和关闭，每次都是一样的步骤，所以将其提取出来:

package com.ssh.jdbc.common;


import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;


public class ConnectionFactory {
private static String driver;
private static String url;
private static String user;
private static String password;

static{
        driver = "com.mysql.jdbc.Driver"; //驱动包名
        url = "jdbc:mysql://127.0.0.1:3306/ssh"; //ssh代表数据库名
        user = "root";  //数据库用户名密码
        password = "root";
//从文件系统中获取参数
    }

/**
 * 获取连接
 * */
public static Connection getConnection() throws Exception {
        Class.forName(driver);//加载mysql的驱动类
return DriverManager.getConnection(url, user, password);
    }

/**
 * 释放资源
 * */
public static void close(ResultSet rs,
            PreparedStatement pstmt ,Connection conn) throws SQLException{
if(rs!=null){
            rs.close();
        }
if(pstmt!=null){
            pstmt.close();
        }
if(conn!=null){
            conn.close();
        }
    }
}

使用时:

package com.ssh.jdbc;


import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.ssh.jdbc.common.ConnectionFactory;

public class Basic {

public void save(Student stu){
        Connection conn = null;
        PreparedStatement pstmt = null;
try {
            conn = ConnectionFactory.getConnection();
            System.out.println(conn);
//3创建pstmt
            String sql = "insert into tbl_student values(null,'"+stu.getName()+"',"+stu.getAge()+")";
            pstmt = conn.prepareStatement(sql);
//4执行sql
int num = pstmt.executeUpdate();
            System.out.println("成功插入"+num);
//5如果有结果集处理结果集
        } catch (Exception e) {
            e.printStackTrace();
        }  finally{
//6释放资源
try {
                ConnectionFactory.close(null, pstmt, conn);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

public void queryAll(){
try {
            Connection conn = null;
            PreparedStatement pstmt = null;
            ResultSet rs = null;
try{
                conn = ConnectionFactory.getConnection();
//创建pstmt对象
                String sql = "select * from tbl_student";
                pstmt = conn.prepareStatement(sql);
//执行查询
                rs = pstmt.executeQuery();
//处理结果集
while(rs.next()){
long id = rs.getLong("id");
                    String name = rs.getString("name");
int age = rs.getInt("age");
                    System.out.println(id+"=="+name+"=="+age);
                }
            }finally{
//释放资源
                ConnectionFactory.close(rs, pstmt, conn);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

/**
 * 更新
 * Student stu (id,name,age)
 * */
public void update(Student stu){
try {
            Connection conn = null;
            PreparedStatement pstmt = null;
try{
                conn = ConnectionFactory.getConnection();
                String sql = "update tbl_student set name = ?,age = ? where id=?";
//预处理sql
                pstmt = conn.prepareStatement(sql);
                pstmt.setString(1, stu.getName());
                pstmt.setInt(2, stu.getAge());
                pstmt.setLong(3, stu.getId());
//执行sql
int num = pstmt.executeUpdate();
                System.out.println("更新成功"+num+"条");
            }finally{
                ConnectionFactory.close(null, pstmt, conn);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

public static void main(String[] args) {
        Basic basic = new Basic();
        Student stu = new Student(1L, "赖瑞", 12);
//basic.save(stu);
//basic.queryAll();
        basic.update(stu);
    }
}