8, mybatisPlus-核心功能

注解

讲解了mybatisplus中使用的注解

1. @TableName --表名注解
2. @TableId --主键注解
3. @TableField --字段注解(非主键)
4. @Version --乐观锁注解、标记 @Verison 在字段上
5. @EnumValue --通枚举类注解(注解在枚举字段上)
6. TableLogic --表字段逻辑处理注解（逻辑删除）
7. @SqlParser --租户注解,支持method上以及mapper接口上
8. @KeySequence --序列主键策略 oracle

核心功能

代码生成器

AutoGenerator 是 MyBatis-Plus 的代码生成器，通过 AutoGenerator 可以快速生成 Entity、Mapper、Mapper XML、Service、Controller 等各个模块的代码，极大的提升了开发效率。

maven依赖

<!-- mp代码生成器依赖 -->
<dependency>
	<groupId>com.baomidou</groupId>
	<artifactId>mybatis-plus-generator</artifactId>
	<version>3.3.2</version>
</dependency>
# MyBatis-Plus 支持 Velocity（默认）、Freemarker、Beetl,非默认需要配置
<dependency>
	<groupId>com.ibeetl</groupId>
	<artifactId>beetl</artifactId>
	<version>3.1.8.RELEASE</version>
</dependency>
<!-- 
<dependency>
	<groupId>org.apache.velocity</groupId>
	<artifactId>velocity-engine-core</artifactId>
	<version>2.2</version>
</dependency>
<dependency>
	<groupId>org.freemarker</groupId>
	<artifactId>freemarker</artifactId>
	<version>2.3.30</version>
</dependency>
-->

代码

代码见mybatisplustest

条件构造器

QueryWrapper

年龄范围, 姓名模糊查询用户

UserService.java

public interface UserService {
	public List<User> selectUsers(String nameLike, Integer maxAge, Integer minAge);
}

UserServiceImpl.java

@Service
public class UserServiceImpl implements UserService {

	@Autowired
	private UserMapper userMapper;
	
	@Override
	public List<User> selectUsers(String nameLike, Integer maxAge, Integer minAge) {
		QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
		queryWrapper.like("name", "xh");
		queryWrapper.between("age", minAge, maxAge);
		List<User> users = userMapper.selectList(queryWrapper);
		return users;
	}

}

运行访问 http://127.0.0.1:8080/user/query/xh-29-10

2020-07-20 15:58:28.263 DEBUG 3784 --- [nio-8080-exec-1] t.i.m.s.mapper.UserMapper.selectList     : ==>  Preparing: SELECT id,name,age,sex FROM User WHERE (name LIKE ? AND age BETWEEN ? AND ?) 
2020-07-20 15:58:28.291 DEBUG 3784 --- [nio-8080-exec-1] t.i.m.s.mapper.UserMapper.selectList     : ==> Parameters: %xh%(String), 10(Integer), 29(Integer)
2020-07-20 15:58:28.322 DEBUG 3784 --- [nio-8080-exec-1] t.i.m.s.mapper.UserMapper.selectList     : <==      Total: 3

UpdateWrapper

将所有sex=0的年龄改为18

UserService.java

public interface UserService {
	public void updateMaleUsers();

    ...
}

UserServiceImpl.java

@Service
public class UserServiceImpl implements UserService {

	@Autowired
	private UserMapper userMapper;
	
	@Override
	public void updateMaleUsers() {
		UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();
		updateWrapper.eq("sex", "0");
		updateWrapper.set("age", 18);
		userMapper.update(null, updateWrapper);
	}

}

UserController.java

@RequestMapping("/update")
	public void update() {
		userService.updateMaleUsers();
	}

运行访问 http://127.0.0.1:8080/user/update

2020-07-20 16:09:28.761 DEBUG 12328 --- [nio-8080-exec-2] t.i.m.s.mapper.UserMapper.update         : ==>  Preparing: UPDATE User SET age=? WHERE (sex = ?) 
2020-07-20 16:09:28.762 DEBUG 12328 --- [nio-8080-exec-2] t.i.m.s.mapper.UserMapper.update         : ==> Parameters: 18(Integer), 0(String)
2020-07-20 16:09:28.775 DEBUG 12328 --- [nio-8080-exec-2] t.i.m.s.mapper.UserMapper.update         : <==    Updates: 2

自定义sql

如果我们需要自己定义sql, 并且想要使用mybatisplus的wapper的便捷, 那该怎么办?

UserWapper.java

@Select("select * from User ${ew.customSqlSegment}")
public List<User> selectByCondition(@Param(Constants.WRAPPER) Wrapper<User> wapper);

UserService.java

/**
 * 更具age查询
 * @param age
 * @return
 */
public List<User> selectByAge(Integer age);

UserServiceImpl.java

@Override
public List<User> selectByAge(Integer age) {
	QueryWrapper<User> queryWrapper = new QueryWrapper<>();
	queryWrapper.eq("age", age);
	return userMapper.selectByCondition(queryWrapper);
}

UserController.java

@RequestMapping("/query/{age}")
public List<User> selectByAge(@PathVariable("age") Integer age){
	List<User> users = userService.selectByAge(age);
	return users;
}

运行访问 http://127.0.0.1:8080/user/query/18

2020-07-20 16:26:59.366 DEBUG 6264 --- [nio-8080-exec-1] t.i.m.s.m.UserMapper.selectByCondition   : ==>  Preparing: select * from User WHERE (age = ?) 
2020-07-20 16:26:59.395 DEBUG 6264 --- [nio-8080-exec-1] t.i.m.s.m.UserMapper.selectByCondition   : ==> Parameters: 18(Integer)
2020-07-20 16:26:59.445 DEBUG 6264 --- [nio-8080-exec-1] t.i.m.s.m.UserMapper.selectByCondition   : <==      Total: 2

mybatisplustest项目地址

mybatis-plus官方教程