MyBatisPlus系列三：增删改查

创建Mapper接口

/**
 * Mapper接口
 * 基于Mybatis:  在Mapper接口中编写CRUD相关的方法  提供Mapper接口所对应的SQL映射文件 以及 方法对应的SQL语句.
 * 基于MP:  让XxxMapper接口继承 BaseMapper接口即可.
 * 		   BaseMapper : 泛型指定的就是当前Mapper接口所操作的实体类类型
 */
public interface EmployeeMapper extends BaseMapper {

}

1、新增测试：

@Test
public void testCommonInsert() {
	//初始化Employee对象
	Employee employee  = new Employee();
	employee.setLastName("MP");
	employee.setEmail("[email protected]");
	employee.setGender(1);
	//insert方法在插入时，会根据实体类的每个属性进行非空判断，只有非空的属性对应的字段才会出现到SQL语句中
	Integer result = employeeMapper.insert(employee);
	System.out.println("result: " + result );
	//insertAllColumn方法在插入时，不管属性是否非空， 属性所对应的字段都会出现到SQL语句中.
	Integer result1 = employeeMapper.insertAllColumn(employee);
	System.out.println("result: " + result1 );
	//获取当前数据在数据库中的主键值
	Integer key = employee.getId();
	System.out.println("key:" + key );
}

控制台输出：

 insert方法：
 Preparing: INSERT INTO tbl_employee ( last_name, email, gender ) VALUES ( ?, ?, ? )    
 Parameters: MP(String), [email protected](String), 1(Integer)
 Updates: 1
 insertAllColumn方法：
 Preparing: INSERT INTO tbl_employee ( last_name,email,gender,age ) VALUES ( ?,?,?,? )   
 Parameters: MP(String), [email protected](String), 1(Integer), null 
 Updates: 1  

报错1：

org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.reflection.ReflectionException: Could not set property 'id' of 'class com.atguigu.mp.beans.Employee' with value '1123462688618409986' Cause: java.lang.IllegalArgumentException: argument type mismatch

原因：没有指定主键生成策略
解决办法：

/**
 * @TableId:
 * 	 value: 指定表中的主键列的列名， 如果实体属性名与列名一致，可以省略不指定.
 *   type: 指定主键策略.
 */
@TableId(value="id" , type =IdType.AUTO)
private Integer id ;

报错2：

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'mybatisplus.employee' doesn't exist

原因：MybatisPlus会默认使用实体类的类名到数据中找对应的表employee
解决办法：

/**
 * MybatisPlus会默认使用实体类的类名到数据中找对应的表.
 */
@TableName(value="tbl_employee")
public class Employee {

也可以在spring配置文件中配置MybatisPlus的全局策略

@TableField注解：

/**
 * 可以不开启驼峰命名。用@TableField注解指定属性对应的数据库字段名
 */
@TableField(value = "last_name")
private String  lastName;
private String  email ;
private Integer gender;
private Integer age ;
/**
 * 指定属性是否在数据库有对应的字段。默认是true
 * 设置为false，在数据库交互时就不会包含在内
 */
@TableField(exist=false)
private Double salary ;

支持主键自增的数据库插入数据获取主键值
 Mybatis: 需要通过 useGeneratedKeys 以及 keyProperty 来设置
 MybatisPlus: 自动将主键值回写到实体类中
2、修改测试：

@Test
public void testCommonUpdate() {
	//初始化修改对象
	Employee employee = new Employee();
	employee.setId(7);
	employee.setLastName("王五");
	employee.setEmail("[email protected]");
	employee.setGender(0);
	//updateById方法在修改时，会根据实体类的每个属性进行非空判断，只有非空的属性对应的字段才会出现到SQL语句中
	Integer result = employeeMapper.updateById(employee);
	System.out.println("result: " + result );
	//updateAllColumnById方法在修改时，不管属性是否非空， 属性所对应的字段都会出现到SQL语句中.
	Integer result1 = employeeMapper.updateAllColumnById(employee);
	System.out.println("result: " + result1 );
}

控制台输出：

updateById方法：
Preparing: UPDATE tbl_employee SET last_name=?, email=?, gender=? WHERE id=? 
Parameters: 王五(String), [email protected](String), 0(Integer), 7(Integer)  (JakartaCommonsLoggingImpl.java:54) 
Updates: 1 
updateAllColumnById方法：
Preparing: UPDATE tbl_employee SET last_name=?,email=?,gender=?,age=? WHERE id=?   
Parameters: 王五(String), [email protected](String), 0(Integer), null, 7(Integer)  
Updates: 1

3、查询测试：

@Test
public void  testCommonSelect() {
	//1. 通过id查询
	Employee employee = employeeMapper.selectById(7);
	System.out.println(employee);

	//2. 通过多个列进行查询。selectOne查询结果只能是一条，否则报错
	Employee  employee1 = new Employee();
	employee.setLastName("王五");
	employee.setGender(0);
	Employee result = employeeMapper.selectOne(employee1);
	System.out.println("result: " +result );

	//3. 通过多个id进行查询
	List idList = new ArrayList<>();
	idList.add(4);
	idList.add(5);
	idList.add(6);
	idList.add(7);
	List emps = employeeMapper.selectBatchIds(idList);
	System.out.println(emps);

    //4. 通过Map封装条件查询。map中的key是数据库中字段名
	Map columnMap = new HashMap<>();
	columnMap.put("last_name", "Tom");
	columnMap.put("gender", 1);
	List emps1 = employeeMapper.selectByMap(columnMap);
	System.out.println(emps1);

	//5. 分页查询
	List emps2 = employeeMapper.selectPage(new Page<>(3, 2), null);
	System.out.println(emps2);
}

控制台输出：

selectById方法：
Preparing: SELECT id AS id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE id=?  
Parameters: 7(Integer)
Total: 1
Employee [id=7, lastName=王五, [email protected], gender=0, age=null]
selectOne方法：
Preparing: SELECT id AS id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE last_name=? AND gender=?
Parameters: 王五(String), 0(Integer)
Total: 1
result: Employee [id=7, lastName=王五, [email protected], gender=0, age=null]
selectBatchIds方法：
Preparing: SELECT id AS id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE id IN ( ? , ? , ? , ? )
Parameters: 4(Integer), 5(Integer), 6(Integer), 7(Integer) 
Total: 4
[Employee [id=4, lastName=White, [email protected], gender=0, age=35], Employee [id=5, lastName=MP, [email protected], gender=1, age=22], Employee [id=6, lastName=MP, [email protected], gender=1, age=22], Employee [id=7, lastName=王五, [email protected], gender=0, age=null]]
selectByMap方法：
Preparing: SELECT id AS id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE gender = ? AND last_name = ?
Parameters: 1(Integer), Tom(String)
Total: 1
[Employee [id=1, lastName=Tom, [email protected], gender=1, age=22]]
selectPage方法：
Preparing: SELECT id AS id,last_name AS lastName,email,gender,age FROM tbl_employee   
Parameters:
[Employee [id=5, lastName=MP, [email protected], gender=1, age=22], Employee [id=6, lastName=MP, [email protected], gender=1, age=22]]

4、删除测试：

@Test
public void testCommonDelete() {
	//1 .根据id进行删除
	Integer result = employeeMapper.deleteById(13);
	System.out.println("result: " + result );

	//2. 根据条件进行删除
	Map columnMap = new HashMap<>();
	columnMap.put("last_name", "MP");
	columnMap.put("email", "[email protected]");
	Integer result1 = employeeMapper.deleteByMap(columnMap);
	System.out.println("result: " + result1 );

	//3. 批量删除
	List idList = new ArrayList<>();
	idList.add(3);
	idList.add(4);
	idList.add(5);
	Integer result2 = employeeMapper.deleteBatchIds(idList);
	System.out.println("result: " + result2 );
}

控制台输出：

deleteById方法：
Preparing: DELETE FROM tbl_employee WHERE id=? 
Parameters: 13(Integer)
Updates: 1
result: 1
deleteByMap方法：
Preparing: DELETE FROM tbl_employee WHERE last_name = ? AND email = ?   
Parameters: MP(String), [email protected](String) 
Updates: 7
result: 7
deleteBatchIds方法：
Preparing: DELETE FROM tbl_employee WHERE id IN ( ? , ? , ? ) 
Parameters: 3(Integer), 4(Integer), 5(Integer)  
Updates: 2
result: 2