项目结构:
User类:
package com.test.mp.mp1111.entity;
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import lombok.Data;
import org.springframework.stereotype.Component;
@Data
public class User {
// @TableId(type = IdType.AUTO)
private Long id;
private Integer age;
private String name;
private String email;
}
UserMapper:
package com.test.mp.mp1111.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.test.mp.mp1111.entity.User;
import lombok.Data;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Repository;
@Component
public interface UserMapper extends BaseMapper<User> {
}
Mp1111ApplicationTests:
package com.test.mp.mp1111;
import com.test.mp.mp1111.entity.User;
import com.test.mp.mp1111.mapper.UserMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import java.util.List;
@SpringBootTest
class Mp1111ApplicationTests {
@Autowired
private UserMapper userMapper;
@Test
public void testUpdateById() {
if (userMapper == null) {
System.out.println("空指针");
}
}
}
项目pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.7.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.test.mp</groupId>
<artifactId>mp1111</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>mp1111</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<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>
<!--mybatis-plus-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.0.5</version>
</dependency>
<!--mysql-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<!--lombok用来简化实体类-->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter</artifactId>
<version>RELEASE</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
我运行Mp1111ApplicationTests中的testUpdateById方法,
显示userMapper为空指针,这是为什么呀