Field testMapper in com.example.demo.service.TestService required a bean of type ‘com.example.demo.m
由于解决过程太漫长,直接给出解决方案:原因mybatis的jar包导错了!Mapper接口类上使用了注解@Mapper,根据intellij idea提示引入了依赖:<dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version..
由于解决过程太漫长,直接给出解决方案:
原因mybatis的jar包导错了!Mapper接口类上使用了注解@Mapper,根据intellij idea提示引入了依赖:
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.3</version>
</dependency>
然后@Mapper可以正常导包,但是会引发一系列的后续问题!
正确的jar包依赖是:
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.1.3</version>
</dependency>
在此记录一下我的解决过程,时间不充足的就没必要往下看了!
问题描述:springboot和mybatis建了个项目,写了个查询,启动项目报错:
Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2020-07-11 09:57:57.829 ERROR 16916 --- [ main] o.s.b.d.LoggingFailureAnalysisReporter :
***************************
APPLICATION FAILED TO START
***************************
Description:
Field testMapper in com.example.demo.service.TestService required a bean of type 'com.example.demo.mapper.TestMapper' that could not be found.
The injection point has the following annotations:
- @org.springframework.beans.factory.annotation.Autowired(required=true)
Action:
Consider defining a bean of type 'com.example.demo.mapper.TestMapper' in your configuration.
Disconnected from the target VM, address: '127.0.0.1:64216', transport: 'socket'
Process finished with exit code 1
我的Mapper接口上添加了@Mapper注解,注解的jar包地址:import org.apache.ibatis.annotations.Mapper;
也没有问题,启动就是报错!
然后我注意到Service中的自动注入dao对象名颜色变红了!我就在注解@Autowired中添加属性值required=false,取消校验,
@Service
public class TestService {
// 添加require=false取消校验对象指针地址
@Autowired(required=false)
private TestMapper testMapper;
public List<Map<String,Object>> getFirstSelect(){
return testMapper.getFirstSelect();
}
}
项目可以正常启动了!心情老高兴了!结果一访问,后台报错:
java.lang.NullPointerException: null
at com.example.demo.service.TestService.getFirstSelect(TestService.java:16) ~[classes/:na]
at com.example.demo.controller.TestController.getFirstSelect(TestController.java:20) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_251]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_251]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_251]
原因:@Mapper注解没起作用,Mapper类TestMapper没有被注册到springioc,导致注入失败,报错空指针!
于是乎换了一种Mapper扫描方式:在启动类上面添加注解@MapperScan(mapper文件包地址),
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
//臊面该包下面所有的mapper文件,和@Mapper注解两者可以二选一
@MapperScan("com.example.demo.mapper")
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
@MapperScan的依赖:
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis-spring</artifactId>
<version>2.0.5</version>
</dependency>
启动后接着报错:
Caused by: java.lang.IllegalArgumentException: Property 'sqlSessionFactory' or 'sqlSessionTemplate' are required
at org.springframework.util.Assert.notNull(Assert.java:198) ~[spring-core-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.mybatis.spring.support.SqlSessionDaoSupport.checkDaoConfig(SqlSessionDaoSupport.java:122) ~[mybatis-spring-2.0.5.jar:2.0.5]
百度原因:缺少依赖!导入下面依赖!
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.0.0</version>
</dependency>
接下来就是个死循环了!哈哈!
如果使用了此依赖,但是此依赖中的jdbc版本太旧了,导致连接不到数据库!
如果使用exclude排除了这个jdbc版本,就重新报错:Property 'sqlSessionFa。。。。。
问题又重新回到了原点!@Mapper!好像无解了!(能力有限)
重新分析原因:结论是jar包有问题!但是正确的jar是什么呢?
好在公司里有成功的spingboot+mybatis项目!pom文件拿来参考了一下!问题解决!
** 贴出一个通过测试运行的pom文件配置,原来的项目找不到了 **
<?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>2.3.1.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example.top</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<!-- 默认达成jar包,部署Tomcat,打成war包 -->
<!--
<packaging>war</packaging>
-->
<name>demo</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-web</artifactId>
<!-- 排除Tomcat的干扰用于打war 包 -->
<!-- <exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
</exclusion>
</exclusions>-->
</dependency>
<!-- <dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<!– 打成war的时候打开注释,本地开发用内嵌tomcat时加上注释 –>
<scope>provided</scope>
</dependency>-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>27.0.1-jre</version>
</dependency>
<!-- mysql 依赖包 -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<!-- 阿里里巴巴的druid连接池 -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.1.16</version>
</dependency>
<!-- mybatis 框架依赖包 -->
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.0.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
</dependency>
<!-- springboot配置redis -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
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