MyBatis-Plus 简单查询

àì夳堔傛蜴生んèń 2022-08-28 10:54 141阅读 0赞

# 一 数据库中的数据 #

# 二 多个 id 的批量查询 #

### 1 测试代码 ###

// 多个id批量查询
    @Test
    public void testSelect1() {
        List<User> users = userMapper.selectBatchIds(Arrays.asList(1, 2, 3));
        System.out.println(users);
    }

### 2 测试结果 ###

Creating a new SqlSession
    SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@42fcc7e6] was not registered for synchronization because synchronization is not active
    2021-10-02 15:41:41.226  INFO 18984 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
    2021-10-02 15:41:42.998  INFO 18984 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
    JDBC Connection [HikariProxyConnection@1693580552 wrapping com.mysql.cj.jdbc.ConnectionImpl@6b3f6585] will not be managed by Spring
    ==>  Preparing: SELECT id,name,age,email,create_time,update_time,version FROM user WHERE id IN ( ? , ? , ? )
    ==> Parameters: 1(Integer), 2(Integer), 3(Integer)
    <==    Columns: id, name, age, email, create_time, update_time, version
    <==        Row: 1, Jone, 18, test1@baomidou.com, null, null, null
    <==        Row: 2, Jack, 20, test2@baomidou.com, null, null, null
    <==        Row: 3, Tom, 28, test3@baomidou.com, null, null, null
    <==      Total: 3
    Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@42fcc7e6]
    [User(id=1, name=Jone, age=18, email=test1@baomidou.com, createTime=null, updateTime=null, version=null), User(id=2, name=Jack, age=20, email=test2@baomidou.com, createTime=null, updateTime=null, version=null), User(id=3, name=Tom, age=28, email=test3@baomidou.com, createTime=null, updateTime=null, version=null)]

# 三 简单条件查询 #

### 1 说明 ###

通过 map 封装查询条件

### 2 注意 ###

map 中的 key 对应数据库中的列名。如：数据库中的字段是 user\_id，实体类中的字段是 userId，这时 map 的 key 需要填写 user\_id

### 3 测试代码 ###

// 简单条件查询
    @Test
    public void testSelect2() {
        Map<String, Object> columnMap = new HashMap<>();
        columnMap.put("name", "Jack");
        columnMap.put("age", 20);
        List<User> users = userMapper.selectByMap(columnMap);
        System.out.println(users);
    }

### 4 测试结果 ###

Creating a new SqlSession
    SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6ae7deac] was not registered for synchronization because synchronization is not active
    2021-10-02 15:45:26.953  INFO 12796 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
    2021-10-02 15:45:28.698  INFO 12796 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
    JDBC Connection [HikariProxyConnection@1633566545 wrapping com.mysql.cj.jdbc.ConnectionImpl@407873d3] will not be managed by Spring
    ==>  Preparing: SELECT id,name,age,email,create_time,update_time,version FROM user WHERE name = ? AND age = ?
    ==> Parameters: Jack(String), 20(Integer)
    <==    Columns: id, name, age, email, create_time, update_time, version
    <==        Row: 2, Jack, 20, test2@baomidou.com, null, null, null
    <==      Total: 1
    Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6ae7deac]
    [User(id=2, name=Jack, age=20, email=test2@baomidou.com, createTime=null, updateTime=null, version=null)]