MyBatisPlus系列六：活动记录ActiveRecord

深碍√TFBOYSˉ_ 2022-04-25 04:54 266阅读 0赞

Active Record(活动记录)，是一种领域模型模式，特点是一个模型类对应关系型数据库中的 一个表，而模型类的一个实例对应表中的一行记录。  
 ActiveRecord 一直广受动态语言（ PHP 、 Ruby 等）的喜爱，而 Java 作为准静态语言， 对于 ActiveRecord 往往只能感叹其优雅，所以 MyBatisPlus也在 AR 道路上进行了一定的探索 。  
1、需要让实体类继承 Model 类且实现主键指定方法

public class Employee extends Model<Employee> {
    	//..fields
    	//..getter and setter
    
    	/**
    	 * 指定当前实体类的主键属性
    	 */
    	@Override
    	protected Serializable pkVal() {
    		return id;
    	} 
    }

测试新增：

@Test
    public void  testARInsert() {
    	Employee employee = new Employee();
    	employee.setLastName("宋老师");
    	employee.setEmail("sls@atguigu.com");
    	employee.setGender(1);
    	employee.setAge(35);
    	boolean result = employee.insert();
    	System.out.println("result:" +result );
    }

控制台输出：

Preparing: INSERT INTO tbl_employee ( last_name, email, gender, age ) VALUES ( ?, ?, ?, ? )   
    Parameters: 宋老师(String), sls@atguigu.com(String), 1(Integer), 35(Integer)
    Updates: 1
    result:true

测试修改：

@Test
    public void testARUpdate() {
    	Employee employee = new Employee();
    	employee.setId(2);
    	employee.setLastName("宋老湿");
    	employee.setEmail("sls@atguigu.com");
    	employee.setGender(1);
    	employee.setAge(36);
    	boolean result = employee.updateById();
    	System.out.println("result:" +result );
    }

控制台输出：

Preparing: UPDATE tbl_employee SET last_name=?, email=?, gender=?, age=? WHERE id=?   
    Parameters: 宋老湿(String), sls@atguigu.com(String), 1(Integer), 36(Integer), 2(Integer)  
    Updates: 1
    result:true

测试查询：

@Test
    public void testARSelect() {
    	Employee employee = new Employee();
    	Employee result = employee.selectById(14);
    	System.out.println("result: " +result );
    	
    	employee.setId(14);
    	Employee result1 = employee.selectById();
    	System.out.println("result: " +result1 );
    	
    	List<Employee> emps = employee.selectAll();
    	System.out.println(emps);
    	
    	List<Employee > emps1= 
    			employee.selectList(new EntityWrapper<Employee>().like("last_name", "老师"));
    	System.out.println(emps1);
    	
    	Integer result2 = employee.selectCount(new EntityWrapper<Employee>().eq("gender", 0));
    	System.out.println("result: " +result2 );
    }

控制台输出：

selectById(14)方法：
    Preparing: SELECT id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE id=?   
    Parameters: 14(Integer) 
    Total: 0
    result: null
    selectById()方法：
    Preparing: SELECT id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE id=?   
    Parameters: 14(Integer)
    Total: 0
    result: null
    selectAll()方法：
    Preparing: SELECT id,last_name AS lastName,email,gender,age FROM tbl_employee   
    Parameters:   
    Total: 4
    [Employee [id=2, lastName=宋老湿, email=sls@atguigu.com, gender=1, age=36], Employee [id=7, lastName=王五, email=xz@sina.com, gender=0, age=null], Employee [id=8, lastName=宋老师, email=sls@atguigu.com, gender=1, age=35], Employee [id=9, lastName=宋老师, email=sls@atguigu.com, gender=1, age=35]]
    selectList方法：
    Preparing: SELECT id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE (last_name LIKE ?)   
    Parameters: %老师%(String)
    Total: 2
    [Employee [id=8, lastName=宋老师, email=sls@atguigu.com, gender=1, age=35], Employee [id=9, lastName=宋老师, email=sls@atguigu.com, gender=1, age=35]]
    selectCount方法：
    Preparing: SELECT COUNT(1) FROM tbl_employee WHERE (gender = ?) 
    Parameters: 0(Integer) 
    Total: 1
    result: 1

测试删除：

/**
     * 注意: 删除不存在的数据 逻辑上也是属于成功的. 
     */
    @Test
    public void testARDelete() {
    	Employee employee = new Employee();
    	boolean result = employee.deleteById(2);
    	System.out.println("result:" +result );
    	
    	employee.setId(2);
    	boolean result1 = employee.deleteById();
    	System.out.println("result:" +result1 );
    	
    	boolean result3 = employee.delete(new EntityWrapper<Employee>().like("last_name", "小"));
    	System.out.println("result:" +result3 );
    }

控制台输出：

deleteById(2)方法：
    Preparing: DELETE FROM tbl_employee WHERE id=? 
    Parameters: 2(Integer) 
    result:true
    deleteById()方法：
    Preparing: DELETE FROM tbl_employee WHERE id=?
    Parameters: 2(Integer) 
    Updates: 0
    result:true
    delete方法：
    Preparing: DELETE FROM tbl_employee WHERE (last_name LIKE ?) 
    Parameters: %小%(String) 
    Updates: 0
    result:true

测试分页：

@Test
    public void  testARPage() {
    	Employee employee = new Employee();
    	Page<Employee> page = employee.selectPage(new Page<>(1, 1), 
    			new EntityWrapper<Employee>().like("last_name", "老"));
    	List<Employee> emps = page.getRecords();
    	System.out.println(emps);
    }

控制台输出：

Preparing: SELECT id,last_name AS lastName,email,gender,age FROM tbl_employee WHERE (last_name LIKE ?)  
    Parameters: %老%(String)
    [Employee [id=8, lastName=宋老师, email=sls@atguigu.com, gender=1, age=35]]