原生mybatisplus只支持一个主键，mpp支持多个字段联合主键增删改查，mapper需要继承MppBaseMapper实体类中联合主键的字段，需要用@MppMultiId注解修饰

在实例类成员变量上使用@MppMultiId表明联合主键

@TableName("test07")
public class Test07Entity {
    @MppMultiId
    @TableField(value = "k1")
    private Integer k1;

    @MppMultiId
    @TableField(value = "k2")
    private String k2;
    
    @TableField(value = "col1")
    private String col1;
    @TableField(value = "col2")
    private String col2;    


mapper需要继承MppBaseMapper
@Mapper

public interface Test07Mapper extends MppBaseMapper<Test07Entity> {
}
​​​​​​​
根据多主键增删改查
    public void testMultiId(){
        //id
        Test07Entity idEntity=new Test07Entity();
        idEntity.setK1(1);
        idEntity.setK2("111");
        //del
        test07Mapper.deleteByMultiId(idEntity);
        //add
        test07Mapper.insert(idEntity);
        //query
        Test07Entity retEntity=test07Mapper.selectByMultiId(idEntity);
        retEntity.setCol1("xxxx");
        //update
        test07Mapper.updateByMultiId(retEntity);
    }