JDBC连接MYSQL,JDBC增删改查 经典 范例

package cn.csdn.dao;

import java.util.List;

import cn.csdn.domain.User;

public interface UserDao {

boolean insert(User entity);
boolean checkUser(String name);
public boolean delete(User entity);
public boolean update(User entity);
User findById(Integer id);
List findAll();
}

package cn.csdn.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import cn.csdn.domain.User;

public class UserDaoImpl implements UserDao{

/*声明操作数据的对象*/
private static Connection conn;
private PreparedStatement pstmt;
private ResultSet rs;

/*静态块*/
static{
/*准备驱动程序,加载驱动*/
try {
Class.forName("com.mysql.jdbc.Driver");
/*面试必考题*/
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/job?user=root&password=admin&useUnicode=true&characterEncoding=UTF-8");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

@Override
public boolean checkUser(String name) {
/*第一步：声明返回变量*/
boolean flag=false;
/*第二步：获取连接对象 conn */
/*第三步：定义sql语句 "select * from user where name='"+name+"'";*/
String sql = "select * from user where name=?";

try {
/*第四步：根据sql语句创建预处理对象*/
pstmt = conn.prepareStatement(sql);
/*第五步：为站位符 赋值*/
int index = 1;
pstmt.setString(index++, name);
/*第六步:执行查询*/
rs = pstmt.executeQuery();
/*第七步:判断*/
if(rs.next()){
flag = true;
}

} catch (SQLException e) {
e.printStackTrace();
}
/*第八步：关闭*/
if(rs!=null){
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

if(pstmt!=null){
try {
pstmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return flag;
}

@Override
public boolean insert(User entity) {
/*第一步：声明返回变量*/
boolean flag=false;
/*第二步：获取连接对象 conn */
/*第三步：定义sql语句 ;insert  into user(name,sex,age)values('"+entity.getName()+"','"+entity.getSex()+"',"+entity.getAge()+");"*/
String sql = "insert  into user(name,sex,age)values(?,?,?);";

try {
/*第四步：根据sql语句创建预处理对象*/
pstmt = conn.prepareStatement(sql);
/*第五步：为站位符 赋值*/
int index = 1;
pstmt.setObject(index++, entity.getName());
pstmt.setObject(index++, entity.getSex());
pstmt.setObject(index++, entity.getAge());
/*第六步:执行更新*/
int i = pstmt.executeUpdate();
/*第七步:判断*/
if(i>0){
flag = true;
}

} catch (SQLException e) {
e.printStackTrace();
}
/*第八步：关闭*/

if(pstmt!=null){
try {
pstmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/*记得一定要把返回的值，修改成返回的变量*/
return flag;
}

@Override
public boolean delete(User entity) {
/*第一步：声明返回变量*/
boolean flag=false;
/*第二步：获取连接对象 conn */
/*第三步：定义sql语句 ;insert  into user(name,sex,age)values('"+entity.getName()+"','"+entity.getSex()+"',"+entity.getAge()+");"*/
String sql = "delete from user where id=?";

try {
/*第四步：根据sql语句创建预处理对象*/
pstmt = conn.prepareStatement(sql);
/*第五步：为站位符 赋值*/
int index = 1;
pstmt.setInt(index++, entity.getId());
/*第六步:执行更新*/
int i = pstmt.executeUpdate();
/*第七步:判断*/
if(i>0){
flag = true;
}

} catch (SQLException e) {
e.printStackTrace();
}
/*第八步：关闭*/

if(pstmt!=null){
try {
pstmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/*记得一定要把返回的值，修改成返回的变量*/
return flag;
}
public static void main(String[] args) {
/*看明白了嘛*/
UserDao userDao = new UserDaoImpl();
/*boolean flag = userDao.checkUser("redarmy");
if(flag){
System.out.println("用户名已经被占用了");
}else{
System.out.println("用户名还没有被使用,你可以使用此用户名");
}*/

/*boolean flag = userDao.insert(new User(null, "红军12", "男", 20));
if(flag){
System.out.println("注册成功");
}else{
System.out.println("注册失败");
}*/

/*List users = userDao.findAll();
for (int i = 0; i < users.size(); i++) {
User entity = (User) users.get(i);
System.out.println(entity.getId()+"  "+entity.getName());
}*/

//userDao.update(new User(7,"孙悟空","女",10000));
User entity = userDao.findById(7);
System.out.println(entity.getId()+"  "+entity.getName());

}

@Override
public List findAll() {
/*第一步:定义返回结果*/
List allentities = new ArrayList();
/*第二步:获取连接对象*/
/*第三步：定义sql语句*/
String sql ="select * from user";
try {
/*第四步：根据sql语句创建预处理对象*/
pstmt = conn.prepareStatement(sql);
/*第五步：为站位符 赋值*/

/*第六步:执行查询*/
rs = pstmt.executeQuery();
/*第七步:判断*/
while(rs.next()){
User entity = new User();
entity.setId(rs.getInt("id"));
entity.setName(rs.getString("name"));
entity.setSex(rs.getString("sex"));
entity.setAge(rs.getInt("age"));
allentities.add(entity);
}

} catch (SQLException e) {
e.printStackTrace();
}
/*第八步：关闭*/
if(rs!=null){
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

if(pstmt!=null){
try {
pstmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return allentities;
}

@Override
public boolean update(User entity) {
/*第一步：声明返回变量*/
boolean flag=false;
/*第二步：获取连接对象 conn */
/*第三步：定义sql语句 ;insert  into user(name,sex,age)values('"+entity.getName()+"','"+entity.getSex()+"',"+entity.getAge()+");"*/
String sql = "update user set name=?,sex=?,age=? where id=?";

try {
/*第四步：根据sql语句创建预处理对象*/
pstmt = conn.prepareStatement(sql);
/*第五步：为站位符 赋值*/
int index = 1;
pstmt.setObject(index++, entity.getName());
pstmt.setObject(index++, entity.getSex());
pstmt.setObject(index++, entity.getAge());
pstmt.setInt(index++, entity.getId());
/*第六步:执行更新*/
int i = pstmt.executeUpdate();
/*第七步:判断*/
if(i>0){
flag = true;
}

} catch (SQLException e) {
e.printStackTrace();
}
/*第八步：关闭*/

if(pstmt!=null){
try {
pstmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/*记得一定要把返回的值，修改成返回的变量*/
return flag;
}

@Override
public User findById(Integer id) {
/*第一步:定义返回结果*/
User entity = new User();
/*第二步:获取连接对象*/
/*第三步：定义sql语句*/
String sql ="select * from user where id=?";
try {
/*第四步：根据sql语句创建预处理对象*/
pstmt = conn.prepareStatement(sql);
/*第五步：为站位符 赋值*/
int index = 1;
pstmt.setInt(index++, id);
/*第六步:执行查询*/
rs = pstmt.executeQuery();
/*第七步:判断*/
if(rs.next()){

entity.setId(rs.getInt("id"));
entity.setName(rs.getString("name"));
entity.setSex(rs.getString("sex"));
entity.setAge(rs.getInt("age"));

}

} catch (SQLException e) {
e.printStackTrace();
}
/*第八步：关闭*/
if(rs!=null){
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

if(pstmt!=null){
try {
pstmt.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return entity;
}

}

package cn.csdn.domain;

import java.io.Serializable;

/*业务Bean*/
public class User implements Serializable{

/**
*
*/
private static final long serialVersionUID = 2646300928284173726L;
/**递增序列*/
private Integer id;
/**姓名*/
private String name;
/*性别*/
private String sex;
/*年龄*/
private Integer age;
public User() {
super();
// TODO Auto-generated constructor stub
}
public User(Integer id, String name, String sex, Integer age) {
super();
this.id = id;
this.name = name;
this.sex = sex;
this.age = age;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}

}