JdbcTemplate的基本使用

1、JdbcTemplate的基本介绍

 JdbcTemplate是Spring对JDBC的封装，目的是使JDBC更加易于使用。JdbcTemplate是Spring的一部分。JdbcTemplate处理了资源的建立和释放。他帮助我们避免一些常见的错误，比如忘了总要关闭连接。他运行核心的JDBC工作流，如Statement的建立和执行，而我们只需要提供SQL语句和提取结果。

Spring为了简化数据库访问，主要做了以下几点工作：

• 提供了简化的访问JDBC的模板类，不必手动释放资源；
• 提供了一个统一的DAO类以实现Data Access Object模式；
• 把SQLException封装为DataAccessException，这个异常是一个RuntimeException，并且让我们能区分SQL异常的原因，例如，DuplicateKeyException表示违反了一个唯一约束；
• 能方便地集成Hibernate、JPA和MyBatis这些数据库访问框架。

2、JdbcTemplate的基本使用

2.1、新增数据（jdbcTemplate.update）

先导入以下依赖包。Spring框架的JdbcTemplate在spring-jdbc的jar包中，，除了要导入这个 jar 包外，还需要导入一个 spring-tx的jar包（它是和事务相关的）。当然连接池的jar包也不能忘记，这里使用的是 druid。

然后在 spring 的 xml 配置文件中配置数据库连接池和 JdbcTemplate，同时我们也开启组件扫描。另外我们可以通过一个  jdbc.properties 配置文件来维护数据库的连接配置。

下面假设我们操作的是 test 数据库里面的 user 表，表结构如下：

jdbc.properties 配置文件内容：

prop.driverClass=com.mysql.jdbc.Driver
prop.url=jdbc:mysql://localhost:3306/test
prop.username=root
prop.password=123456

spring 的 xml 配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
                           http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    <!--开启组件扫描-->
    <context:component-scan base-package="test, service, dao"></context:component-scan>

    <!--引入外部配置文件-->
    <context:property-placeholder location="classpath:jdbc.properties"/>

    <!--配置数据库连接池-->
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="${prop.driverClass}"></property>  <!--通过${}使用外部配置文件的值-->
        <property name="url" value="${prop.url}"></property>
        <property name="username" value="${prop.username}"></property>
        <property name="password" value="${prop.password}"></property>
    </bean>

    <!-- 配置JdbcTmplate -->
    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <!-- 注入dataSource -->
        <property name="dataSource" ref="dataSource"></property>
        <!-- <constructor-arg name="dataSource" ref="dataSource"></constructor-arg>-->  <!-- 也可以用构造函数写法 -->
    </bean>
</beans>

新建一个实体类 User ：

package entity;

public class User {
    private int id;
    private String name;
    private String password;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

新建一个 UserServiceImpl 类：

package service;

import dao.UserDao;
import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserServiceImpl implements UserService{
    @Autowired
    private UserDao userDao;

    @Override
    public void addUser(User user) {
        userDao.addUser(user);
    }
}

新建一个 UserDaoImpl 类：

package dao;

import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

@Repository
public class UserDaoImpl implements UserDao{
    //注入JdbcTemplate
     @Autowired
    private JdbcTemplate jdbcTemplate;

    @Override
    public void addUser(User user) {
        //创建SQL语句
        String sql = "insert into user values(?, ?, ?)";
        //调用方法执行SQL
        int updateRow = jdbcTemplate.update(sql, user.getId(), user.getName(), user.getPassword());
        
        System.out.println(updateRow);
    }

}

验证代码：

package test;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.jdbc.core.JdbcTemplate;
import entity.User;
import service.UserService;
import service.UserServiceImpl;

public class Test01 {
    ApplicationContext ioc = new ClassPathXmlApplicationContext("bean01.xml");
    //JdbcTemplate jdbcTemplate= ioc.getBean(JdbcTemplate.class);   //我们也可以直接通过获取到的jdbctemplate进行SQL操作，上面使用UserServiceImpl和UserDaoImpl只是为了更符合MVC分层的规范

    @Test
    public void test1() {
        User user = new User();
        user.setId(5);
        user.setName("AA");
        user.setPassword("112233");

        UserService userService = ioc.getBean(UserServiceImpl.class);
        userService.addUser(user);   //执行增加方法
    }
}

执行上面 test1 方法，可以看到输出如下：

 即对一行数据起了作用，可以看到表数据发生了更改：

2.1.1、批量增加（batchUpdate）

批量增加可以使用 jdbcTemplate.batchUpdate() 方法，示例如下：

UserServiceImpl 增加批量增加方法：

package service;

import dao.UserDao;
import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserServiceImpl implements UserService{
    @Autowired
    private UserDao userDao;

    @Override
    public void addBath(List<Object[]> userList) {
        userDao.addBath(userList);
    }
}

UserDaoImpl 增加批量增加方法：

package dao;

import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

import java.util.Arrays;
import java.util.List;

@Repository
public class UserDaoImpl implements UserDao {
    //注入JdbcTemplate
    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Override
    public void addBath(List<Object[]> userList) {
        String sql = "insert into user values(?, ?, ?)";
        int[] ints = jdbcTemplate.batchUpdate(sql, userList);  //batchUpdate方法第二个参数是集合，该集合元素是数组，数组里面的每个值对应着添加到数据库表里面的字段值。该方法返回影响行数数组

        System.out.println(Arrays.toString(ints));
    }
}

验证：

package test;

import entity.User;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import service.UserService;
import service.UserServiceImpl;

import java.util.ArrayList;
import java.util.List;

public class TestMain {
    ApplicationContext ioc = new ClassPathXmlApplicationContext("bean01.xml");

    @Test
    public void test2() {
        List<Object[]> userList = new ArrayList<>();
        Object[] arr1 = {1, "name1", "password1"};
        Object[] arr2 = {2, "name2", "password2"};
        Object[] arr3 = {3, "name3", "password3"};

        userList.add(arr1);
        userList.add(arr2);
        userList.add(arr3);

        UserService userService = ioc.getBean(UserServiceImpl.class);
        userService.addBath(userList);
    }
}

2.2、修改和删除数据（jdbcTemplate.update）

修改和删除跟上面的新增操作一样，只是SQL语句不同而已。

UserServiceImpl 增加修改和删除方法：

package service;

import dao.UserDao;
import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserServiceImpl implements UserService{
    @Autowired
    private UserDao userDao;

    @Override
    public void updateUser(User user) {
        userDao.updateUser(user);
    }

    @Override
    public void deleteUser(int userId) {
        userDao.deleteUser(userId);
    }
}

UserDaoImpl 增加修改删除方法：

package dao;

import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

@Repository
public class UserDaoImpl implements UserDao{
    //注入JdbcTemplate
     @Autowired
    private JdbcTemplate jdbcTemplate;

    @Override
    public void updateUser(User user) {
        String sql = "update user set name=?, password=? where id=?";
        int updateRow = jdbcTemplate.update(sql, user.getName(), user.getPassword(), user.getId());
        System.out.println(updateRow);
    }

    @Override
    public void deleteUser(int userId) {
        String sql = "delete from user where id=?";
        int updateRow = jdbcTemplate.update(sql, userId);
        System.out.println(updateRow);
    }

}

验证代码：

package test;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;import entity.User;
import service.UserService;
import service.UserServiceImpl;public class Test01 {
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean01.xml");

    //修改操作
    @Test
    public void test1() {
        User user = new User();
        user.setId(2);
        user.setName("AA");
        user.setPassword("112233");

        UserService userService = applicationContext.getBean(UserServiceImpl.class);
        userService.updateUser(user);
    }

    //删除操作
    @Test
    public void test2() {
        UserService userService = applicationContext.getBean(UserServiceImpl.class);
        userService.deleteUser(5);
    }
}

2.2.1、批量修改和删除（batchUpdate）

批量修改和批量删除都可以使用 jdbcTemplate.batchUpdate() 方法，示例如下：

UserServiceImpl 增加批量修改和删除方法：

package service;

import dao.UserDao;
import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserServiceImpl implements UserService{
    @Autowired
    private UserDao userDao;

    //批量修改
    @Override
    public void updateBatch(List<Object[]> listArg) {
        userDao.updateBatch(listArg);
    }

    //批量删除
    @Override
    public void deleteBath(List<Object[]> listArg) {
        userDao.deleteBath(listArg);
    }
}

UserDaoImpl 增加批量修改和删除方法：

package dao;

import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

import java.util.Arrays;
import java.util.List;

@Repository
public class UserDaoImpl implements UserDao {
    //注入JdbcTemplate
    @Autowired
    private JdbcTemplate jdbcTemplate;

    //批量修改
    @Override
    public void updateBatch(List<Object[]> listArg) {
        String sql = "update user set name=?, password=? where id=?";
        int[] ints = jdbcTemplate.batchUpdate(sql, listArg);
        System.out.println(Arrays.toString(ints));
    }

    //批量删除
    @Override
    public void deleteBath(List<Object[]> listArg) {
        String sql = "delete from user where id=?";
        int[] ints = jdbcTemplate.batchUpdate(sql, listArg);
        System.out.println(Arrays.toString(ints));
    }
}

验证：

package test;

import entity.User;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import service.UserService;
import service.UserServiceImpl;

import java.util.ArrayList;
import java.util.List;

public class TestMain {
    ApplicationContext ioc = new ClassPathXmlApplicationContext("bean01.xml");

    //批量修改
    @Test
    public void test3() {
        List<Object[]> userList = new ArrayList<>();
        Object[] arr1 = {"name1changed", "password1", 1};
        Object[] arr2 = {"name2changed", "password2", 2};
        Object[] arr3 = {"name3changed", "password3", 3};

        userList.add(arr1);
        userList.add(arr2);
        userList.add(arr3);

        UserService userService = ioc.getBean(UserServiceImpl.class);
        userService.updateBatch(userList);
    }

    //批量删除
    @Test
    public void test4() {
        List<Object[]> userList = new ArrayList<>();
        Object[] arr1 = {6};
        Object[] arr2 = {7};

        userList.add(arr1);
        userList.add(arr2);

        UserService userService = ioc.getBean(UserServiceImpl.class);
        userService.deleteBath(userList);
    }

}

2.3、查询数据

2.3.1、查询返回某个值（queryForObject）

比如查询 user 表内数据总数：

package service;

import dao.UserDao;
import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserServiceImpl implements UserService{
    @Autowired
    private UserDao userDao;

    @Override
    public int getUserCount() {
        return userDao.getUserCount();
    }
}

UserDaoImpl 代码：

package dao;

import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

@Repository
public class UserDaoImpl implements UserDao{
    //注入JdbcTemplate
     @Autowired
    private JdbcTemplate jdbcTemplate;

    @Override
    public int getUserCount() {
        String sql = "select count(*) from user";
        int userCount = jdbcTemplate.queryForObject(sql, int.class);  //第二个参数是返回类型的class
        return userCount;
    }

}

验证：

package test;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import entity.User;
import service.UserService;
import service.UserServiceImpl;

public class Test01 {
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean01.xml");

    //查询数量
    @Test
    public void test4() {
        UserService userService = applicationContext.getBean(UserServiceImpl.class);
        int userCount = userService.getUserCount();
        System.out.println(userCount);   //将输出user表内数据总数
    }
}

2.3.2、查询返回对象（queryForObject）

比如查询 user 表内某一条数据，然后我们可以将该数据封装成一个 User 对象：

package service;

import dao.UserDao;
import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserServiceImpl implements UserService{
    @Autowired
    private UserDao userDao;

    @Override
    public User getUserInfo(int userId) {
        return userDao.getUserInfo(userId);
    }
}

UserDaoImpl 代码：

package dao;

import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

@Repository
public class UserDaoImpl implements UserDao{
    //注入JdbcTemplate
     @Autowired
    private JdbcTemplate jdbcTemplate;

    @Override
    public User getUserInfo(int userId) {
        String sql = "select * from user where id=?";
        // rowMapper 是一个接口，可以使用这个接口里面的实现类完成数据的封装，规定每一行记录和JavaBean的属性如何映射
        User user = jdbcTemplate.queryForObject(sql, new BeanPropertyRowMapper<>(User.class), userId);
        return user;
    }

}

验证：

package test;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import entity.User;
import service.UserService;
import service.UserServiceImpl;

public class Test01 {
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean01.xml");

    @Test
    public void test3() {
        UserService userService = applicationContext.getBean(UserServiceImpl.class);
        User user = userService.getUserInfo(2);
        System.out.println(user.getName());
    }
}

2.3.2、查询返回集合（query）

比如查询 user 表内的所有数据，并且将数据都封装成 User 对象：

package service;

import dao.UserDao;
import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserServiceImpl implements UserService{
    @Autowired
    private UserDao userDao;

    @Override
    public List<User> getAllUser() {
        return userDao.getAllUser();
    }
}

UserDaoImpl 代码：

package dao;

import entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
public class UserDaoImpl implements UserDao{
    //注入JdbcTemplate
     @Autowired
    private JdbcTemplate jdbcTemplate;

    @Override
    public List<User> getAllUser() {
        String sql = "select * from user";
        List<User> userList = jdbcTemplate.query(sql, new BeanPropertyRowMapper<>(User.class));
        return userList;
    }

}

验证：

package test;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import entity.User;
import service.UserService;
import service.UserServiceImpl;

import java.util.List;

public class Test01 {
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean01.xml");

    //查询全部数据
    @Test
    public void test5() {
        UserService userService = applicationContext.getBean(UserServiceImpl.class);
        List<User> userList = userService.getAllUser();
        for (User user: userList) {
            System.out.println(user.getName());
        }
    }
}