Spring Boot integrates MyBatis-Plus to implement CRUD operations

This article will demonstrate how to integrate in Spring Boot projectsMyBatis-PlusFramework, quickly implement database addition, deletion, modification and search operations. Compared with native MyBatis, MyBatis-Plus provides a cleaner API and automation capabilities.

Environmental preparation

JDK 1.8+
MySQL 5.7+
Spring Boot 2.
MyBatis-Plus 3.

Implementation steps

1. Create a project and add dependencies

When creating a project through Spring Initializr, check:

Spring Web
MySQL Driver

Add MyBatis-Plus dependencies manually (）：

<dependency>
    <groupId></groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.3.1</version>
</dependency>

2. Configure database connection ()

spring:
  datasource:
    driver-class-name: 
    url: jdbc:mysql://localhost:3306/mp_demo?useSSL=false&amp;serverTimezone=Asia/Shanghai
    username: root
    password: 123456

mybatis-plus:
  configuration:
    log-impl:  # Enable SQL logging  global-config:
    db-config:
      id-type: assign_id # Primary key generation strategy (using snowflake algorithm)

3. Create entity class

@Data
@TableName("t_user") // Specify the table namepublic class User {
    @TableId(type = IdType.ASSIGN_ID) // Snowflake algorithm generates ID    private Long id;
    private String username;
    private Integer age;
    private String email;
}

4. Create a Mapper interface

@Mapper
public interface UserMapper extends BaseMapper&lt;User&gt; {
    //Inheriting BaseMapper, the basic CRUD method is included}

5. Implement Service layer (optional enhancement)

@Service
public class UserService {
    @Autowired
    private UserMapper userMapper;

    // Insert    public int addUser(User user) {
        return (user);
    }

    // Query all    public List&lt;User&gt; getAllUsers() {
        return (null);
    }

    // Conditional query    public User getUserById(Long id) {
        return (id);
    }

    // renew    public int updateUser(User user) {
        return (user);
    }

    // delete    public int deleteUser(Long id) {
        return (id);
    }
}

6. Add paging plugin configuration

@Configuration
public class MybatisPlusConfig {
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        (new PaginationInnerInterceptor());
        return interceptor;
    }
}

7. Create Controller

@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired
    private UserService userService;

    @PostMapping
    public String add(@RequestBody User user) {
        (user);
        return "Insert successfully";
    }

    @GetMapping("/{id}")
    public User getById(@PathVariable Long id) {
        return (id);
    }

    @GetMapping("/list")
    public List&lt;User&gt; list() {
        return ();
    }

    @PutMapping
    public String update(@RequestBody User user) {
        (user);
        return "Update Successfully";
    }

    @DeleteMapping("/{id}")
    public String delete(@PathVariable Long id) {
        (id);
        return "Delete successfully";
    }
}

Test Example

Insert data (POST /user)

{
    "username": "Zhang San",
    "age": 25,
    "email": "zhangsan@"
}

Pagination query (need to customize the method)

// Add in Mapper:@Select("SELECT * FROM t_user WHERE age &gt; #{age}")
Page&lt;User&gt; selectPageByAge(Page&lt;User&gt; page, @Param("age") Integer age);

// Controller call:@GetMapping("/page")
public Page&lt;User&gt; page(@RequestParam(defaultValue = "1") Integer pageNum,
                      @RequestParam(defaultValue = "10") Integer pageSize) {
    Page&lt;User&gt; page = new Page&lt;&gt;(pageNum, pageSize);
    return (page, null);
}

Key Feature Description

Automatically generate SQL: No need to write XML files, basic CRUD is automatically implemented

Primary Key Policy:supportAUTO(Database is increased by itself),ASSIGN_ID(Snowflake Algorithm),UUIDwait

Conditional constructor:passQueryWrapperBuild complex query conditions

QueryWrapper&lt;User&gt; wrapper = new QueryWrapper&lt;&gt;();
("username", "open").lt("age", 30);
(wrapper);

Frequently Asked Questions

Mapper not found when starting error

Make sure to add the startup class@MapperScan("")
Check whether the Mapper interface is marked@Mapperannotation

Field mapping failed

Check whether the database field name complies with the camel to underscore rule
use@TableField(value = "db_column")Specify field map

Pagination invalid

Confirm that the paging plugin configuration has been added
The query method parameters must bePageObject

Extension suggestions

useCode GeneratorQuickly generate Entity/Mapper/Service code
CombinedLambdaQueryWrapperImplement type-safe query conditions
pass@VersionImplement optimistic locking function

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