java.lang.ClassNotFoundException：找不到实现
java.lang.ClassNotFoundException: Cannot find implementation for
我需要帮助解决以下错误：
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userController' defined in file [D:\projects\PIK\bin\main\edu\pw\eiti\pik\user\UserController.class]: Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [edu.pw.eiti.pik.user.UserController]: Constructor threw exception; nested exception is java.lang.RuntimeException: java.lang.ClassNotFoundException: Cannot find implementation for edu.pw.eiti.pik.user.UserMapper
at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:278) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1270) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1127) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:545) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:502) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean[=11=](AbstractBeanFactory.java:312) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:310) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:200) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:760) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:868) ~[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:752) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:388) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:327) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1246) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1234) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at edu.pw.eiti.pik.PikApplication.main(PikApplication.java:10) [main/:na]
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [edu.pw.eiti.pik.user.UserController]: Constructor threw exception; nested exception is java.lang.RuntimeException: java.lang.ClassNotFoundException: Cannot find implementation for edu.pw.eiti.pik.user.UserMapper
at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:182) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:117) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:271) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
... 18 common frames omitted
Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: Cannot find implementation for edu.pw.eiti.pik.user.UserMapper
at org.mapstruct.factory.Mappers.getMapper(Mappers.java:79) ~[mapstruct-jdk8-1.2.0.Final.jar:na]
at edu.pw.eiti.pik.user.UserMapper.getInstance(UserMapper.java:12) ~[main/:na]
at edu.pw.eiti.pik.user.UserController.<init>(UserController.java:18) ~[main/:na]
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_111]
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_111]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_111]
at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_111]
at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:170) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
... 20 common frames omitted
Caused by: java.lang.ClassNotFoundException: Cannot find implementation for edu.pw.eiti.pik.user.UserMapper
at org.mapstruct.factory.Mappers.getMapper(Mappers.java:93) ~[mapstruct-jdk8-1.2.0.Final.jar:na]
at org.mapstruct.factory.Mappers.getMapper(Mappers.java:76) ~[mapstruct-jdk8-1.2.0.Final.jar:na]
... 27 common frames omitted
UserMapper 接口有
@Mapper(unmappedTargetPolicy = ReportingPolicy.IGNORE)
注释。
我将 eclipse Neon 与 buildship 插件一起使用，org.mapstruct 和 spring 是用 Gradle 导入的。
它在我同事的 IntelliJ
上没有这个错误
UserMapper 代码：
package edu.pw.eiti.pik.user;
import org.mapstruct.Mapper;
import org.mapstruct.ReportingPolicy;
import org.mapstruct.factory.Mappers;
import org.springframework.security.core.GrantedAuthority;
@Mapper(unmappedTargetPolicy = ReportingPolicy.IGNORE)
public interface UserMapper {
static UserMapper getInstance() {
return Mappers.getMapper(UserMapper.class);
}
User fromDto(UserDto dto);
UserDto toDto(User entity);
Authority fromDto(AuthorityDto dto);
AuthorityDto toDto(GrantedAuthority entity);
}
根据我的阅读，它可能会导致编译器无法连接自动生成的代码（Gradle 未在 AnnotationProcessing>FactoryPath 中设置任何内容）
将 Mapstruct 与 Spring 一起使用时，您可以定义映射器应使用 componentModel 生成 Spring bean，如 2. Set up. 2.4 Configuration options.
中所述
@Mapper(unmappedTargetPolicy = ReportingPolicy.IGNORE, componentModel = "spring")
public interface UserMapper {
/* your code... */
}
这允许您在 bean 中注入映射器：
@RestController
public class UserController {
@Autowired
private UserMapper userMapper;
//rest of your code...
}
考虑到 Mapstruct 在预编译阶段生成代码，因此在编译代码并查看生成的代码文件夹之前，您不会看到任何 class 实现 UserMapper 接口。
找到可能的原因：
https://github.com/mapstruct/mapstruct/issues/1159
看起来像是 mapstruct 和 lombok 之间的问题
编辑：
解决方案是从 eclipse.ini 中删除 javaagent:lombok.jar，重新启动 IDE 并重建项目，复制注释生成的文件，将 javaagent 添加到 eclipse.ini , 重新启动 IDE 并重建项目并恢复复制的文件
将注释 mapstruct 和 lombok 处理器添加到您的编译器插件，mapstruct 应该为您的映射器接口生成实现：
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.6.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<annotationProcessorPaths>
<path>
<groupId>org.mapstruct</groupId>
<artifactId>mapstruct-processor</artifactId>
<version>${org.mapstruct.version}</version>
</path>
<path>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${org.projectlombok.version}</version>
</path>
</annotationProcessorPaths>
</configuration>
</plugin>
我需要帮助解决以下错误：
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userController' defined in file [D:\projects\PIK\bin\main\edu\pw\eiti\pik\user\UserController.class]: Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [edu.pw.eiti.pik.user.UserController]: Constructor threw exception; nested exception is java.lang.RuntimeException: java.lang.ClassNotFoundException: Cannot find implementation for edu.pw.eiti.pik.user.UserMapper
at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:278) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1270) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1127) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:545) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:502) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean[=11=](AbstractBeanFactory.java:312) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:310) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:200) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:760) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:868) ~[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:752) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:388) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:327) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1246) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1234) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at edu.pw.eiti.pik.PikApplication.main(PikApplication.java:10) [main/:na]
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [edu.pw.eiti.pik.user.UserController]: Constructor threw exception; nested exception is java.lang.RuntimeException: java.lang.ClassNotFoundException: Cannot find implementation for edu.pw.eiti.pik.user.UserMapper
at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:182) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:117) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:271) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
... 18 common frames omitted
Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: Cannot find implementation for edu.pw.eiti.pik.user.UserMapper
at org.mapstruct.factory.Mappers.getMapper(Mappers.java:79) ~[mapstruct-jdk8-1.2.0.Final.jar:na]
at edu.pw.eiti.pik.user.UserMapper.getInstance(UserMapper.java:12) ~[main/:na]
at edu.pw.eiti.pik.user.UserController.<init>(UserController.java:18) ~[main/:na]
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_111]
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_111]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_111]
at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_111]
at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:170) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
... 20 common frames omitted
Caused by: java.lang.ClassNotFoundException: Cannot find implementation for edu.pw.eiti.pik.user.UserMapper
at org.mapstruct.factory.Mappers.getMapper(Mappers.java:93) ~[mapstruct-jdk8-1.2.0.Final.jar:na]
at org.mapstruct.factory.Mappers.getMapper(Mappers.java:76) ~[mapstruct-jdk8-1.2.0.Final.jar:na]
... 27 common frames omitted
UserMapper 接口有
@Mapper(unmappedTargetPolicy = ReportingPolicy.IGNORE)
注释。 我将 eclipse Neon 与 buildship 插件一起使用，org.mapstruct 和 spring 是用 Gradle 导入的。 它在我同事的 IntelliJ
上没有这个错误UserMapper 代码：
package edu.pw.eiti.pik.user;
import org.mapstruct.Mapper;
import org.mapstruct.ReportingPolicy;
import org.mapstruct.factory.Mappers;
import org.springframework.security.core.GrantedAuthority;
@Mapper(unmappedTargetPolicy = ReportingPolicy.IGNORE)
public interface UserMapper {
static UserMapper getInstance() {
return Mappers.getMapper(UserMapper.class);
}
User fromDto(UserDto dto);
UserDto toDto(User entity);
Authority fromDto(AuthorityDto dto);
AuthorityDto toDto(GrantedAuthority entity);
}
根据我的阅读，它可能会导致编译器无法连接自动生成的代码（Gradle 未在 AnnotationProcessing>FactoryPath 中设置任何内容）
将 Mapstruct 与 Spring 一起使用时，您可以定义映射器应使用 componentModel 生成 Spring bean，如 2. Set up. 2.4 Configuration options.
@Mapper(unmappedTargetPolicy = ReportingPolicy.IGNORE, componentModel = "spring")
public interface UserMapper {
/* your code... */
}
这允许您在 bean 中注入映射器：
@RestController
public class UserController {
@Autowired
private UserMapper userMapper;
//rest of your code...
}
考虑到 Mapstruct 在预编译阶段生成代码，因此在编译代码并查看生成的代码文件夹之前，您不会看到任何 class 实现 UserMapper 接口。
找到可能的原因：
https://github.com/mapstruct/mapstruct/issues/1159
看起来像是 mapstruct 和 lombok 之间的问题
编辑：
解决方案是从 eclipse.ini 中删除 javaagent:lombok.jar，重新启动 IDE 并重建项目，复制注释生成的文件，将 javaagent 添加到 eclipse.ini , 重新启动 IDE 并重建项目并恢复复制的文件
将注释 mapstruct 和 lombok 处理器添加到您的编译器插件，mapstruct 应该为您的映射器接口生成实现：
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.6.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<annotationProcessorPaths>
<path>
<groupId>org.mapstruct</groupId>
<artifactId>mapstruct-processor</artifactId>
<version>${org.mapstruct.version}</version>
</path>
<path>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${org.projectlombok.version}</version>
</path>
</annotationProcessorPaths>
</configuration>
</plugin>