First, the public field is automatically populated Profile

As the name suggests: that is, when inserting or updating data, if the data item is not set, the default values will be filled

Here it will involve metadata processing interface and its two methods:

com.baomidou.mybatisplus.mapper.MetaObjectHandler
insertFill (MetaObject as Metaobject) This method is inserted in the data automatically populated when the logical method
updateFill (MetaObject metaObject) This method is to update the data logic automatically populated when the method of

And MetaObject This class is a wrapper object MyBatis provides for better access to information related to the object.

Second, the common field is automatically populated configured as follows

2.1, add annotations for the entity attributes required to automatically fill

public class User {
     @TableId(type=IdType.AUTO)
     private Integer id;
     @TableField (Fill = FieldFill.INSERT_UPDATE) // when inserted and will update the field that filling 
     Private String name;
     @TableLogic   // flag is a logical symbol for 
     Private Integer deleteFlag;
         
     // set methods
     // get methods
｝

@TableFiled annotation fill this property offers three Autofill settings

2.2, create a class that inherits MetaObjectHandler

The method to achieve the appropriate, how to automatically fill in the insert and update data logic

public class MyMetaObjectHandler extends MetaObjectHandler{
    
    // logical method for automatically filling insertion 
    @Override
     public  void insertFill (MetaObject as Metaobject) {
         // the TODO Auto-Generated Stub Method 
        System.out.println ( "Method ### calls insertFill ###" );
        
        Object obj = getFieldValByName("name", metaObject);
        if (obj == null) {
            setFieldValByName ( "name", "filling insert Test" , as Metaobject);
        }
    }
    // logical method for automatically updating the filling 
    @Override
     public  void updateFill (MetaObject as Metaobject) {
         // the TODO Auto-Generated Stub Method 
        System.out.println ( "Method ### calls updateFill ###" );
        Object obj = getFieldValByName("name", metaObject);
        if (obj == null) {
            setFieldValByName ( "name", "Update fill Test" , as Metaobject);
        }
    }
}

2.3, is configured in the configuration file applicationContext.xml

<-! MyBatis-PLUS global configuration policies, thus avoiding the repeated use of annotations in each entity configuration -> 
    < the bean ID = "globalConfiguration" class = "com.baomidou.mybatisplus.entity.GlobalConfiguration" > 
        < Property name = "dbColumnUnderline" value = "to true" > </ Property >   <! - the default configuration database underscore version 2.3 -> 
        <! - Specifies the database ID generation strategy 0: increment database -> 
        < Property name = " idtype " value =" 0 " > </ Property > 
        <-! specified database table prefix ->
        <property name="tablePrefix" value="tbl_"></property>
        <!-- 注入处理器方法 -->
        <property name="metaObjectHandler" ref="myMetaObjectHandler"></property>
    </bean>
    <!-- 注入处理器的bean -->
    <bean id="myMetaObjectHandler" class="cn.hjj.mp.handler.MyMetaObjectHandler"></bean>

2.4, the following test code

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:applicationContext.xml"})
public class TestMetaObjectHandler {
    @Autowired
    private UserMapper userMapper;
    @Test
    public void testInsert() {
        User user = new User();
        user.setDeleteFlag(1);
        userMapper.insert(user);
    }
    
    @Test
    public  void testUpdate () {
        User user = new User();
        user.setId(4);
        user.setDeleteFlag(1);
        userMapper.updateById(user);
    }
}

On learning MyBatis-Plus public field is automatically populated