MyBatis Plus 2.3 个人笔记-02-基本注解

• 实体类注解

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

    private static final long serialVersionUID = 1L;

    /*
	 * @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.  ID_WORKER 全局唯一ID，内容为空自动填充（默认配置）
	 */
    @TableId(value = "id", type = IdType.ID_WORKER)
    private Long id;

    private String lastName;

    private String email;

    private String gender;

    private Integer age;

    /**
     * 声明该属性不是数据库中字段
     */
    @TableField(exist = false)
    private String notExist;

}
/* 省略get set */

• 使用通用CURD方法
  • 　　删除

	/**
	 * 通用 删除操作
	 */
	@Test
	public void testCommonDelete() {
		//1 .根据id进行删除
		Integer result = employeeMapper.deleteById(13);


/*
==>  Preparing: DELETE FROM tbl_employee WHERE id=? 
==> Parameters: 13(Long)
<==    Updates: 0
*/

		
		//2. 根据 条件进行删除
//		Map<String,Object> columnMap = new HashMap<>();
//		columnMap.put("last_name", "MP");
//		columnMap.put("email", "mp@atguigu.com");
//		Integer result = employeeMapper.deleteByMap(columnMap);
//		System.out.println("result: " + result );

/*
==>  Preparing: DELETE FROM tbl_employee WHERE last_name = ? AND email = ? 
==> Parameters: MP(String), mp@atguigu.com(String)
<==    Updates: 0
*/


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

/*
==>  Preparing: DELETE FROM tbl_employee WHERE id IN ( ? , ? , ? ) 
==> Parameters: 35(Integer), 45(Integer), 55(Integer)
<==    Updates: 0
*/

条件构造器

实体包装器，用于处理 sql 拼接，排序，实体参数查询等！

补充说明： 使用的是数据库字段，不是Java属性!

	/**
	 * 条件构造器  删除操作
	 *
	 */
	@Test
	public void testEntityWrapperDelete() {

		employeeMapper.delete(
				new EntityWrapper<Employee>()
						.eq("last_name", "Tom")
						.eq("age", 22)
		);
	}


/*
==>  Preparing: DELETE FROM tbl_employee WHERE (last_name = ? AND age = ?) 
==> Parameters: Tom(String), 22(Integer)
<==    Updates: 0
*/

• • 　　修改
    

    ---

	/**
	 * 通用 更新操作
	 */
	@Test
	public void testCommonUpdate() {
		//初始化修改对象
		Employee employee = new Employee();
		employee.setId(7L);
		employee.setLastName("小泽老师");
		employee.setEmail("xz@sina.com");
		employee.setGender("0");

　　　　　　　　　 // updateById 实体类为空的列 自动跳出，不修改
		Integer result = employeeMapper.updateById(employee);

/*
==>  Preparing: UPDATE tbl_employee SET last_name=?, email=?, gender=? WHERE id=? 
==> Parameters: 小泽老师(String), xz@sina.com(String), 0(String), 7(Long)
<==    Updates: 0
*/
　　　　　　　　　 // updateAllColumnById 所有列都会修改
		Integer result = employeeMapper.updateAllColumnById(employee);

/*
==>  Preparing: UPDATE tbl_employee SET last_name=?,email=?,gender=?,age=?,version=? WHERE id=? 
==> Parameters: 小泽老师(String), xz@sina.com(String), 0(String), null, null, 7(Long)
<==    Updates: 0
*/

	}

	/**
	 * 条件构造器  修改操作
	 */
	@Test
	public void testEntityWrapperUpdate() {

		Employee employee = new Employee();
		employee.setLastName("苍老师");
		employee.setEmail("cls@sina.com");
		employee.setGender("0");


		employeeMapper.update(employee,
				new EntityWrapper<Employee>()
						.eq("last_name", "Tom")
						.eq("age", 44)
		);


/*
==>  Preparing: UPDATE tbl_employee SET last_name=?, email=?, gender=? WHERE (last_name = ? AND age = ?) 
==> Parameters: 苍老师(String), cls@sina.com(String), 0(String), Tom(String), 44(Integer)
<==    Updates: 0
*/


	}

• • 　　　新增

	/**
	 * 通用 插入操作
	 */
	@Test
	public void testCommonInsert() {

		//初始化Employee对象
		Employee employee  = new Employee();
		employee.setLastName("MP");
		employee.setEmail("mp@atguigu.com");
		//employee.setGender(1);
		//employee.setAge(22);
		//employee.setSalary(2"0""0""0""0"."0");
		//插入到数据库   
		// 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);  

/*
==>  Preparing: INSERT INTO tbl_employee ( id, last_name, email ) VALUES ( ?, ?, ? ) 
==> Parameters: 1107953008443265026(Long), MP(String), mp@atguigu.com(String)
<==    Updates: 1
*/



		//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 result = employeeMapper.insertAllColumn(employee);

/*
==>  Preparing: INSERT INTO tbl_employee ( id,last_name,email,gender,age,version ) VALUES ( ?,?,?,?,?,? ) 
==> Parameters: 1107952717069209602(Long), MP(String), mp@atguigu.com(String), null, null, null
<==    Updates: 1
*/



		System.out.println("result: " + result );

		//获取当前数据在数据库中的主键值 mybatis plus自动会回填id
		Long key = employee.getId();
		System.out.println("key:" + key );
	}

• • 　　查询

	/**
	 * 通用 查询操作
	 */
	@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    id  +  lastName
//		Employee  employee = new Employee();
//		//employee.setId(7);
//		employee.setLastName("小泽老师");
//		employee.setGender("0");
//		
//		Employee result = employeeMapper.selectOne(employee);
//		System.out.println("result: " +result );


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

		//4. 通过Map封装条件查询
//		Map<String,Object> columnMap = new HashMap<>();
//		columnMap.put("last_name", "Tom");
//		columnMap.put("gender", 1);
//		
//		List<Employee> emps = employeeMapper.selectByMap(columnMap);
//		System.out.println(emps);

		//5. 分页查询
		List<Employee> emps = employeeMapper.selectPage(new Page(1, 2), null);
		System.out.println(emps);
	}

	/**
	 * 条件构造器   查询操作
	 */
	@Test
	public void testEntityWrapperSelect() {
		//我们需要分页查询tbl_employee表中，年龄在18~5"0"之间且性别为男且姓名为Tom的所有用户

//		List<Employee> emps =employeeMapper.selectPage(new Page<Employee>(1, 2),
//					new EntityWrapper<Employee>()
//					.between("age", 18, 5"0")
//					.eq("gender", 1)
//					.eq("last_name", "Tom")
//				);
//		System.out.println(emps);


/*
==>  Preparing: SELECT COUNT(1) FROM tbl_employee WHERE (age BETWEEN ? AND ? AND gender = ? AND last_name = ?) 
==> Parameters: 18(Integer), 50(Integer), 1(Integer), Tom(String)
<==    Columns: COUNT(1)
<==        Row: 0
==>  Preparing: SELECT id AS id,last_name AS lastName,email,gender,age,version FROM tbl_employee WHERE (age BETWEEN ? AND ? AND gender = ? AND last_name = ?) 
==> Parameters: 18(Integer), 50(Integer), 1(Integer), Tom(String)
<==      Total: 0
*/



		// 查询tbl_employee表中， 性别为女并且名字中带有"老师" 或者  邮箱中带有"a"

//		List<Employee> emps = employeeMapper.selectList(
//				new EntityWrapper<Employee>()
//				.eq("gender", "0")
//				.like("last_name", "老师")
//				//.or()    // SQL: (gender = ? AND last_name LIKE ? OR email LIKE ?)    
//				.orNew()   // SQL: (gender = ? AND last_name LIKE ?) OR (email LIKE ?) 
//				.like("email", "a")
//				);
//		System.out.println(emps);


/*
==>  Preparing: SELECT id AS id,last_name AS lastName,email,gender,age,version FROM tbl_employee WHERE (gender = ? AND last_name LIKE ?) OR (email LIKE ?) 
==> Parameters: 0(String), %老师%(String), %a%(String)
<==    Columns: id, lastName, email, gender, age, version
<==        Row: 1107952717069209602, MP, mp@atguigu.com, null, null, null
<==        Row: 1107953008443265026, MP, mp@atguigu.com, null, null, null
<==      Total: 2
*/


		// 查询性别为女的, 根据age进行排序(asc/desc), 简单分页

//		List<Employee> emps  = employeeMapper.selectList(
//				new EntityWrapper<Employee>()
//				.eq("gender", "0")
//				.orderBy("age")
//				//.orderDesc(Arrays.asList(new String [] {"age"}))
//				.last("desc limit 1,3")
//				);
//		System.out.println(emps);

	}


/*
==>  Preparing: SELECT id AS id,last_name AS lastName,email,gender,age,version FROM tbl_employee WHERE (gender = ?) ORDER BY age desc limit 1,3 
==> Parameters: 0(String)
<==      Total: 0
*/

•  源码: https://github.com/youxiu326/sb_mybatis_puls2.3