brief introduction

MyBatis-Plus (MP) is a MyBatis enhancement tool. It is based on MyBatis only to enhance without changing. It is born to simplify development and improve efficiency.

Characteristic

1. Non-intrusive: only enhance without change, introduce it will not affect existing projects, such as silky smooth
2. Low loss: Automatically inject basic CURD at startup, without loss of performance and direct object-oriented operation
3. Powerful CRUD operation: Built-in general Mapper, general Service, only through a small amount of configuration can achieve most CRUD operation of single form, more powerful conditional constructor, to meet all kinds of use needs
4. Support for Lambda Formal Call: Through Lambda expression, it is convenient to write all kinds of query conditions without worrying about field errors.
5. Support multiple databases: support MySQL, MariaDB, Oracle, DB2, H2, HSQL, SQLite, Postgre, SQL Server 2005, SQL Server and other databases
6. Support for automatic generation of primary keys: support up to four primary key strategies (including distributed unique ID generator - Sequence), free configuration, perfect solution to the primary key problem
7. Support for XML Hot Loading: Mapper's corresponding XML supports hot loading, and for simple CRUD operations, it can even be started without XML.
8. Supporting ActiveRecord Mode: Supporting ActiveRecord Formal Calls, Entity Classes can perform powerful CRUD operations simply by inheriting Model Classes
9. Support for custom global generic operations: support for global generic method injection (Write once, use anywhere)
10. Support for automatic keyword escalation: support database keywords (order, key...) Auto-escaping and customizing keywords
11. Built-in Code Generator: Using code or Maven plug-in can quickly generate Mapper, Model, Service, Controller layer code, support template engine, and more customized configuration for you to use.
12. Built-in Paging Plug-in: Based on MyBatis physical paging, developers do not need to care about specific operations. After configuring the plug-in, writing paging is equivalent to ordinary List queries.
13. Built-in Performance Analysis Plug-in: It can output Sql statements and their execution time. It is recommended that this function be enabled when developing tests to quickly pull out slow queries.
14. Built-in global interception plug-in: provide full table delete, update operation intelligent analysis blocking, also can customize interception rules to prevent misoperation
15. Built-in Sql injection stripper: support Sql injection stripping, effectively prevent Sql injection attacks

Configuration with SpringBook Project
Introduce the father project first

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.3.RELEASE</version>
    <relativePath/>
</parent>

Introduce spring-boot-starter, spring-boot-starter-test, mybatis-plus-boot-starter, lombok, h2 dependencies:

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.0.1</version>
    </dependency>
    <dependency>
        <groupId>com.h2database</groupId>
        <artifactId>h2</artifactId>
        <scope>runtime</scope>
    </dependency>
</dependencies>

To configure
Adding H2-related configuration to applcation.yml file

spring:
  datasource:
    driver-class-name: org.h2.Driver
    schema: classpath:db/schema-h2.sql
    data: classpath:db/data-h2.sql
    url: jdbc:h2:mem:test
    username: root
    password: test

Scanning Mapper files with the @MapperScan annotation on the spring boot boot boot boot class

@SpringBootApplication
@MapperScan("Your own mapper File address")
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(QuickStartApplication.class, args);
    }
}

Code
Write the entity class user.java

@Data
public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;
}

Write userMapper.java

public interface UserMapper extends BaseMapper<User> {
}

test

@RunWith(SpringRunner.class)
@SpringBootTest
public class SampleTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testSelect() {
        System.out.println(("----- selectAll method test ------"));
        List<User> userList = userMapper.selectList(null);
        Assert.assertEquals(5, userList.size());
        userList.forEach(System.out::println);
    }
}

The selectList method in UserMapper has a parameter of MP's built-in conditional wrapper Wrapper, so there are no conditions without filling it in.