Quick start

  1. Create database mybatis-plus

  2. Create table

DROP TABLE IF EXISTS user;
CREATE TABLE user
(
id BIGINT(20) NOT NULL COMMENT 'primary key ID',
name VARCHAR(30) NULL DEFAULT NULL COMMENT 'name',
age INT(11) NULL DEFAULT NULL COMMENT 'age',
email VARCHAR(50) NULL DEFAULT NULL COMMENT 'email'.PRIMARY KEY (id)
);
INSERT INTO user (id, name, age, email) VALUES
(1.'Jone'.18.'[email protected]'),
(2.'Jack'.20.'[email protected]'),
(3.'Tom'.28.'[email protected]'),
(4.'Sandy'.21.'[email protected]'),
(5.'Billie'.24.'[email protected]');
-- In real development, version (optimistic lock), deleted (logical deletion), gmT_create, gmt_Modified
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  1. Initialize the project using SpringBoot
  2. Import dependence
<dependency>
  <groupId>com.baomidou</groupId>
  <artifactId>mybatis-plus-boot-starter</artifactId>
  <version>3.0. 5</version>
</dependency>
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  1. Connect to the database! This step is the same as mybatis!
spring.datasource.username=root
spring.datasource.password=ccc+022599
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/mybatis_plus? useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai
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  1. Write POJOs and Mapper
@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
  private Long id;
  private String name;
  private Integer age;
  private String email;
}
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package cn.ccb.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import cn.ccb.pojo.User;
import org.springframework.stereotype.Repository;

@Mapper
@Repository
public interface UserMapper extends BaseMapper<User> {
    // BaseMapper inherits all methods from its parent class
    // All CRUD operations have been written
}
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test

@SpringBootTest
class MybatisPlusApplicationTests {
  
  @Autowired
  private UserMapper userMapper;
  @Test
  void contextLoads(a) {
    // The argument is a Wrapper, conditional constructor, we don't need null here
    // Query all users
    List<User> users = userMapper.selectList(null); users.forEach(System.out::println); }}Copy the code

To configure the log

mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl
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Primary key generation policy

  1. @tableId on entity class field (type = idType.auto)

    @TableId(type =IdType.AUTO )// Primary key policy
private Long id;
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    public enum IdType {
  AUTO(0), // The database ID is automatically increased
  NONE(1), // The primary key is not set
  ID_WORKER(3), // The default global unique ID
  UUID(4), // Globally unique ID UUID
}
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  2. The database primary key field must be self-increment

Automatic filling

  1. Add annotations to entity class field attributes
// Add padding to the field
@TableField(fill = FieldFill.INSERT)
private Date createTime;
@TableField(fill = FieldFill.INSERT_UPDATE)
private Date updateTime;
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  1. Write a processor to handle this annotation!
package cn.ccb.handler;

import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.reflection.MetaObject;
import org.springframework.stereotype.Component;

import java.util.Date;

@Slf4j
@Component
public class MyMetaObjectHandler implements MetaObjectHandler {

    // Fill the policy when inserting
    @Override
    public void insertFill(MetaObject metaObject) {
        this.setFieldValByName("createTime".new Date(),metaObject);
        this.setFieldValByName("updateTime".new Date(),metaObject);
    }

    // Update the policy
    @Override
    public void updateFill(MetaObject metaObject) {
        this.setFieldValByName("updateTime".newDat(),metaObject); }}Copy the code

Test insert, update, and observe the time!

Optimistic locking

Implementation method:

  • When the record is fetched, the current version is retrieved
  • When performing an update, set version = newVersion where version = oldVersion
  • If the version is incorrect, the update fails
Optimistic lock: Obtain the version number version =1


// Thread A completes an operation on A resource first, when version = 2
update user set name = "kuangshen", version = version + 1    
where id = 2 and version = 1
    

update user set name = "kuangshen", version = version + 1
where id = 2 and version = 1 // Version has changed to 2. Thread B fails
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Test MP’s optimistic lock plugin

  1. Add version field to database!

  2. Entity class plus corresponding field

    @Version // Optimistic lock Version annotation
private Integer version;
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  3. To register the plugin

    @Configuration / / configuration class
public class MyBatisPlusConfig {
    
  @Bean
  public OptimisticLockerInterceptor optimisticLockerInterceptor(a) {
    return newOptimisticLockerInterceptor(); }}Copy the code

Logic to delete

Physical delete: Removes a logical delete from a database directly: invalidates a variable instead of removing it from the database! deleted = 0 => deleted = 1

Administrators can view deleted records! Prevent data loss!

  1. Add a deleted field to the data table
  2. Add attributes to the entity class
@TableLogic  // Logical delete
private Integer deleted;
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  1. configuration
// Remove the component logically
@Bean
public ISqlInjector iSqlInjector(a){
    return new LogicSqlInjector();
}
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# logical delete
mybatis-plus.global-config.db-config.logic-delete-value=1
mybatis-plus.global-config.db-config.logic-not-delete-value=0
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  1. Remove front:

  1. To delete

  1. After deleting

The record is still in the database, but the value has changed!

Code generator

Dao, POJO, service and Controller are all written by me! AutoGenerator is the code generator of MyBatis-Plus, through which the code of Entity, Mapper, Mapper XML, Service, Controller and other modules can be generated quickly. Greatly improved the development efficiency.

public class CodeGenerator {
    public static void main(String[] args) {
        AutoGenerator mpg = new AutoGenerator();

        // Global configuration
        GlobalConfig gc = new GlobalConfig();
        String projectPath = System.getProperty("user.dir");
        gc.setOutputDir(projectPath + "/src/main/java");
        gc.setOpen(false);
        gc.setSwagger2(true); // Open swagger annotation

        gc.setServiceName("%sService");
        mpg.setGlobalConfig(gc);

        // Set the data source
        DataSourceConfig dsc = new DataSourceConfig();
        dsc.setDbType(DbType.MYSQL);
        dsc.setDriverName("com.mysql.cj.jdbc.Driver");
        dsc.setUsername("root");
        dsc.setPassword("ccc+022599");
        dsc.setUrl("jdbc:mysql://localhost:3306/mybatis_plus? useUnicode=true&serverTimezone=Asia/Shanghai&characterEncoding=utf-8");
        mpg.setDataSource(dsc);

        / / package configuration
        PackageConfig pc = new PackageConfig();
        pc.setParent("cn.tony");
        pc.setModuleName("student");
        pc.setEntity("pojo");
        mpg.setPackageInfo(pc);

        // Policy configuration
        StrategyConfig strategy = new StrategyConfig();
        ** strategy.setInclude("sys_teacher","sys_stu","user"); /** strategy.setInclude("sys_teacher","sys_stu","user"); Only these three tables are mapped */
        strategy.setInclude();
        
        /* If the table name and field name are underlined, the name is humped */
        strategy.setNaming(NamingStrategy.underline_to_camel);
        strategy.setColumnNaming(NamingStrategy.underline_to_camel);
        strategy.setEntityLombokModel(true);
        strategy.setLogicDeleteFieldName("deleted");

        // Auto-fill
        TableFill gmtCreate = new TableFill("gmt_create", FieldFill.INSERT);
        TableFill gmtModified = new TableFill("gmt_modified", FieldFill.INSERT_UPDATE);
        ArrayList<TableFill> tableFills = new ArrayList<>();
        tableFills.add(gmtCreate);
        tableFills.add(gmtModified);
        strategy.setTableFillList(tableFills);
        / / optimistic locking
        strategy.setVersionFieldName("version");
        strategy.setRestControllerStyle(true);
        strategy.setControllerMappingHyphenStyle(true); mpg.setStrategy(strategy); mpg.execute(); }}Copy the code