1. Primary key policy

@tabelid (type = idtype.assign_id)

  • ASSIGN_ID is adopted by twitterSnowflakes algorithm, a randomly generated 19-bit ID
  • AUTO Indicates the AUTO increase policy

2. Automatic filling

@ TableField (FieldFill. INSERT)

  • Create time can use this

@ TableField (FieldFill INSERT_UPDATE)

  • Change the time with this

Label the class @compoent

Usage:

  • Create a handler package, create a class and implement the MetaObjectHandler interface

  • There are two methods in the interface

    • InsertFill (MetaObject) This method is called when an operation is added

      • Call the method this.setFieldValByName(“createTime”, new Date(), metaObject)
      • Call the method this.setFieldValbyName (“updateTime”, new Date(), metaObject)

    • Update (MetaObject) This method is invoked when MetaObject is performing modification operations

      • Call the method this.setFieldValbyName (“updateTime”, new Date(), metaObject)

3. Optimistic locking

Add the Version field, which defaults to 1

  • The first session

Compares the current modified data version with the database version

After the operation is complete, the data version number is updated from 1 to 2

  • The second session

If you get an incorrect version number, the operation fails

3.1 Code Implementation

  • Add a field to the table as the version number, and add attributes to the corresponding entity class

  • Add @vesion and @tablefeild (fieldfill.insert) to the attributes of the entity class

  • Added again in the insertFill method of the interface

    • this.setFieldValByName(“version”, 1, metaObject)

  • Add Configuration classes to the Configuration package and add @Configuration and @mapperscan (” “)

@Bean
public OptimisticLockerInterceptor optimisticLockerInterceptor(a){
    return new OptimisticLockerInterceptor();
}
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4. Query operations

4.1 Batch Querying Multiple ids

List list = Mapper.selectBatchIds(Arrays.asList(1.2.3))
// Query information based on ids 1, 2, and 3
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4.2 Querying Information Based on Conditions

new HashMap();
map.put("name"."fq")
map.put("age".20)
Mapper.selectByMap(map);
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4.3 Paging Query

Add the plug-in

Write paging code

  • Plugin Page object, passing in two parameters (current Page, record Page per Page)
  • Call mp method for paging
Page<Fq> page = new Page(1.3);
Page<Fq> fqPage = Mapper.selectPage(page,null);

long Pages = fqPage.getPages();/ / the total number of pages
long current = fqPage.getcurrent();/ / the current page
List<Fq> recodes = fqPage.getRecords();// Query data set
Long total = fqPage.getTotal();// Total number of records
boolean hasNext = fqPage.hasNext();// Is there a next page
boolean hasPrevious = fqPage.hasPrevious();// check if there is a previous page

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5. Delete the vm

5.1 Logical Deletion

Add a field to the table as a logical drop flag, changing the flag bit each time it is deleted

  • 0 indicates that the data is not deleted
  • 1 indicates logical deletion

5.2 Logical Deletion Operations

  • Add fields to the tabledelete
  • Add attributes to the entity classdeleteAnd add @tablelogic and @tablefeild (fill = FieldFill.INSERT)
  • Add the initial value this.setFieldValByName(“delete”, 0, metaObject) to insertFill in Hanlder

The update method is used underneath