Mybatis数据连接池的配置---增删改查（以及遇见的问题）

1.首先创建项目和各个文件，如图所示：

2.配置相关数据库连接

在jdbc.properties中加入

1 db.driver=com.mysql.jdbc.Driver
2 db.url=jdbc:mysql://localhost:3306/mysql?characterEncoding=utf8&useSSL=false&serverTimezone=Asia/Shanghai&rewriteBatchedStatements=true
3 db.username=root
4 db.password=xiaopan
5 db.maxActive=10
6 db.initialSize=2

注意，用户名和密码，还有数据库名换成你自己的。

3.创建MybaticConfig数据库配置类。

package com.config;

import com.alibaba.druid.pool.DruidDataSource;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

import javax.sql.DataSource;
@MapperScan(basePackages = "com.mapper")//自动查找mapper接口，并且创建接口实例
@Configuration
@PropertySource("classpath:jdbc.properties")
public class MybatisConfig {
@Value("${db.driver}") String driver;
    @Value("${db.url}") String url;
    @Value("${db.username}") String username;
    @Value("${db.password}") String password;
    @Value("${db.maxActive}") int maxActive;
    @Value("${db.initialSize}") int initialSize;

    /*
    数据库连接的配置信息
     */
    @Bean
    public DataSource dataSource(){
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(driver);
        dataSource.setUrl(url);
        dataSource.setUsername(username);
        dataSource.setPassword(password);
        dataSource.setMaxActive(maxActive);
        dataSource.setInitialSize(initialSize);
        return dataSource;
    }

    /*
    mybatis的核心功能的工厂，需要将数据连接池datasource注入给它。
     */
    @Bean
    public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);//注入
        return bean.getObject();
    }
}

！！！发现此处连接数据库mysql太复杂了，我们直接导入一个Druid依赖，自动导入数据源（配置信息）以及mysql的连接驱动包

然后在配置文件（application.yml）中写入数据

# mysql
spring:
  profiles:
    active: dev  #激活application-dev.yml文件
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driverClassName: com.mysql.jdbc.Driver
  jackson:
    time-zone: GMT+8
    date-format: yyyy-MM-dd HH:mm:ss
  # 模板实时刷新
  thymeleaf:
    cache: false
    prefix:
      classpath: /templates
  servlet:
    multipart:
      location: images/
  resources:
    static-locations: classpath:static/,file:${spring.servlet.multipart.location}

 application-dev.yml配置文件

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/animal?serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf-8
    username: root
    password: xiaopan
    #连接池的配置信息
    initialSize: 10
    minIdle: 10
    maxActive: 100
    maxWait: 60000
    timeBetweenEvictionRunsMillis: 300000
    minEvictableIdleTimeMillis: 3600000
    validationQuery: SELECT 1 FROM DUAL
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    poolPreparedStatements: true
    maxPoolPreparedStatementPerConnectionSize: 20

4.进行数据库连接测试

--创建一个测试类TestCase

 --在测试类中写入以下代码

import com.config.MybatisConfig;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;

public class TestCase {
    AnnotationConfigApplicationContext ctx;
    @Before
    public void init(){
        ctx= new AnnotationConfigApplicationContext(MybatisConfig.class);
    }
    @After
    public void destroy(){
        ctx.close();
    }
    @Test
    public void testDataSource(){
        DataSource ds = ctx.getBean("dataSource",DataSource.class);
        String sql = "select 'hello world'";
        try(Connection conn = ds.getConnection()){
            Statement s = conn.createStatement();
            ResultSet rs = s.executeQuery(sql);
            while(rs.next()){
                System.out.println(rs.getString(1));
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

 点击测试，出现对应的hello world在控制台中。

 5.创建mybatis映射文件

---首先声明数据库访问接口DemoMapper

package com.mapper;

import org.apache.ibatis.annotations.Select;

public interface DemoMapper {
    @Select("select 'hello world!'")
    String hello();
}

 6.测试类中测试@select注解，Mybatis能否正确处理sql语句。

  @Test
    public void testHelloWorld() {
        DemoMapper mapper = ctx.getBean("demoMapper", DemoMapper.class);
        String str = mapper.hello();
        System.out.println(str);
    }

可以看到控制台中正确输出了 Mybatis接口中hello()方法-- hello world！

--------------------------------------------------------------------------------此处Mybatis已经可以正确应用 --------------------------------------------------------------------------------------------------------

现在我们用数据库来操刀

1.创建数据库的信息。

 /*创建数据库和表*/
 create database tedu_ums
use tedu_ums;
CREATE table t_user(
    id int auto_increment comment '用户id',
    username varchar(20) UNIQUE not null COMMENT '用户名',
    pwd varchar(20) not null COMMENT '密码',
    age int COMMENT '年龄',
    phone varchar(20) COMMENT '手机号码',
    email varchar(20) COMMENT '电子邮箱',
    PRIMARY key(id),

    )DEFAULT CHARSET=UTF8;
/*向数据库插入数据*/
 insert into t_user(username,pwd,phone,age,email)
        values("zs01",'1234','13838383800',28,'zs01@163.com'),
        ("zs02",'1234','13838383801',27,'zs02@163.com'),
        ("zs03",'1234','13838383802',26,'zs03@163.com'),
        ("zs04",'1234','13838383803',25,'zs04@163.com'),
        ("zs05",'1234','13838383804',24,'zs05@163.com'),
        ("zs06",'1234','13838383805',23,'zs06@163.com'),
        ("zs07",'1234','13838383806',22,'zs07@163.com'),
        ("zs08",'1234','13838383807',21,'zs08@163.com'),
      ("zs09",'1234','13838383808',20,'zs09@163.com'),
        ("zs10",'1234','13838383809',19,'zs10@163.com')

2.创建 entity实体类  去和数据库中的 属性 对应。

User实体类代码：

package com.entity;

/*
实体类
 */
public class User {
    private Integer id;
    private String username;
    private String pwd;
    private Integer age;
    private String phone;
    private String email;

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", pwd='" + pwd + '\'' +
                ", age=" + age +
                ", phone='" + phone + '\'' +
                ", email='" + email + '\'' +
                '}';
    }

    public User() {
    }

    public User(Integer id, String username, String pwd, Integer age, String phone, String email) {
        this.id = id;
        this.username = username;
        this.pwd = pwd;
        this.age = age;
        this.phone = phone;
        this.email = email;
    }

    public Integer getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

3.创建Mybatis接口层--UserMapper类（！！！此处有注意事项！！！）

package com.mapper;

import com.entity.User;
import org.apache.ibatis.annotations.*;

import java.util.List;

public interface UserMapper {
    /*注意事项一：在Mybatis中使用sql语句的时候，如果参数超过了一个，需要用到@Param(value="phone")注解进行声明参数，
     不然编译生成的class文件是没有对应的这个参数的
     */

    //注意事项二：不建议用*去查询数据库，此处虽然可以select *
    @Select("select id,username,pwd,age,phone,email from t_user where id=#{id}")
    User findUserById(Integer id);
    @Select("select id,username,pwd,age,phone,email from t_user ")
    List<User> findAllUser();
    /*
    增加数据
     */
    @Insert("insert into t_user(id,username,pwd,age,phone,email) "
            +"values(#{id},#{username},#{pwd},#{age},#{phone},#{email})")
//    @Options(useGeneratedKeys = true,keyProperty = "id")//设置id不自增。
    Integer insert(User user);
    /*
    更改方式1
     */
    @Update("update t_user set username=#{username},pwd=#{pwd},age=#{age},"+
            "phone=#{phone},email=#{email} where  id=#{id}")
    int updateUser(User user);
    /*
    更改方式2 （参数超过了一个使用）
     */
    @Update("update t_user set phone=#{phone},email=#{email} where id=#{id}")
    int updateUser1(@Param(value="phone") String phone, @Param(value="email") String email, @Param(value="id") int id);
    /*
    数据库删除(注意事项三：删除语句中的from不能去掉)
     */
    @Delete("delete from t_user where id=#{id}")
    int deleteUser(Integer id);
}

4.测试类的方法

import com.config.MybatisConfig;
import com.entity.User;
import com.mapper.DemoMapper;
import com.mapper.UserMapper;
import org.apache.ibatis.session.SqlSessionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.List;

public class TestCase {
    AnnotationConfigApplicationContext ctx;

    @Before
    public void init() {
        ctx = new AnnotationConfigApplicationContext(MybatisConfig.class);
    }

    @After
    public void destroy() {
        ctx.close();
    }

    @Test
    public void testDataSource() {
        DataSource ds = ctx.getBean("dataSource", DataSource.class);
        String sql = "select 'hello world'";
        try (Connection conn = ds.getConnection()) {
            Statement s = conn.createStatement();
            ResultSet rs = s.executeQuery(sql);
            while (rs.next()) {
                System.out.println(rs.getString(1));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Test
    public void testSqlSessionFactory() {
        SqlSessionFactory factory = ctx.getBean("sqlSessionFactory", SqlSessionFactory.class);
        System.out.println(factory);
    }

    @Test
    public void testHelloWorld() {
        DemoMapper mapper = ctx.getBean("demoMapper", DemoMapper.class);
        String str = mapper.hello();
        System.out.println(str);
    }

    /*
    数据库查找：根据id查找
     */
    @Test
    public void testFindUserById() {
        UserMapper userMapper = ctx.getBean("userMapper", UserMapper.class);
        User user = userMapper.findUserById(31);
        System.out.println(user);
    }

    /*
    数据库查找：查找全部。
    */
    @Test
    public void testFindAllUser() {
        UserMapper userMapper = ctx.getBean("userMapper", UserMapper.class);
        List<User> user = userMapper.findAllUser();
        System.out.println(user);
    }

    /*
    数据库插入
     */
    @Test
    public void testInsertUser() {
        User user = new User(null, "99", "1", 1, "1", "1");
        UserMapper userMapper = ctx.getBean("userMapper", UserMapper.class);
        int insert = userMapper.insert(user);
        System.out.println(insert);
    }

    /*
    数据库更改方式1
     */
    @Test
    public void testUpdateUser() {
        UserMapper userMapper = ctx.getBean("userMapper", UserMapper.class);
        User user = userMapper.findUserById(31);
        System.out.println("修改前：" + user);
        user.setAge(100);
        int update = userMapper.updateUser(user);
        User user1 = userMapper.findUserById(31);
        System.out.println("修改后：" + user1);
    }

    /*
    数据库更改方式2
     */
    @Test
    public void testUpadateUser1() {
        UserMapper userMapper = ctx.getBean("userMapper", UserMapper.class);
        int update = userMapper.updateUser1("110", "220", 100);
        System.out.println(update);
    }

    /*
    数据库删除
     */
    @Test
    public void testDeleteUser() {
        UserMapper userMapper = ctx.getBean("userMapper", UserMapper.class);
        int delete = userMapper.deleteUser(100);
        System.out.println(delete);
    }

    /**
     * 配置文件xml整合Mybatis----测试
     */
    @Test
    public void testTest() {
        DemoMapper mapper = ctx.getBean("demoMapper", DemoMapper.class);
        String str = mapper.test();
        System.out.println(str);
    }
}

用配置文件的话，要将MybatisConfig配置文件中的——mybatis的核心功能的工厂——部分的代码换成如下：

/*
    mybatis的核心功能的工厂，需要将数据连接池datasource注入给它。
     */
    @Bean
    public SqlSessionFactory sqlSessionFactory(DataSource dataSource,
    @Value("classpath:mappers/*.xml") Resource[] mapperLocations//第二个属性是xml文件配置所需要的
    ) throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);//注入
        bean.setMapperLocations(mapperLocations);//xml文件操作数据库所需要的注入
        return bean.getObject();
    }

 创建整合Mybatis的——xml配置文件：

总结：做这个的时候，遇到了几个问题

①在接口层写方法的时候，遇到了（注意事项）的问题，往上翻注释查阅。

②为什么在MybatisConfig中删去@Configuration这个注解还能有效的装配实例类（就是为什么@Bean还能用）？

个人理解：因为在测试类中，用到了AnnotationConfigApplicationContext这个类方法，

　　　　　初始化spring的时候装配了MybatisConfig这个类，然后用getBean的方法装配了对应的类对象（例如此处的：DataSource）

mysql的连接驱动包