在 Spring Boot 中使用 ModelMapper 映射列表集合时的问题答案

【问题标题】：Issue when mapping Collection of List using ModelMapper in Spring Boot在 Spring Boot 中使用 ModelMapper 映射列表集合时的问题
【发布时间】：2020-06-20 21:47:00
【问题描述】：

我有一个 Project 域，我想使用 modelmapper 将其映射到 ProjectDTO。项目域包含一个位置列表。在 DTO 中，我不想要 Location 域，只想要位置的 id。

public class Project {
   private List<Location> locations
}

public class Location {
   private Long id;
   private String name;
}

public class ProjectDTO {
   private List<Long> assignedLocations;   
}

于是我按照Link的教程，创建了一个自定义转换器：

public Converter<List<Location>, List<Long>> locationToLongConverter = new Converter<List<Location>, List<Long>>() {

        @Override
        public List<Long> convert(MappingContext<List<Location>, List<Long>> context) {
            List<Location> source = context.getSource();
            List<Long> destination = context.getDestination();
            
            for (Location location : source) {
                destination.add(location.getId());
            }
            
            return destination;
        }       
    
    };

然后，我创建了 PropertyMap 来告诉 modelmapp 使用该字段的转换器：

PropertyMap<Project, ProjectDTO> itemDTOMap = new PropertyMap<Project, ProjectDTO>() {

    @Override
    protected void configure() {
        using(locationToLongConverter).map(source.getLocations()).setAssignedLocations(null);
    }
};

最后，我在我的 SpringBootApplication 类中创建了一个 bean：

@Bean
public ModelMapper modelMapper() {
    ModelMapper mapper =  new ModelMapper();
    mapper.addMappings(projectConverter.getItemDTOMap());
    return mapper;
}

但它不起作用，启动应用程序时出现错误。

nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.modelmapper.ModelMapper]: Factory method 'modelMapper' threw exception; nested exception is org.modelmapper.ConfigurationException: ModelMapper configuration errors:

1) Failed to configure mappings

1 error
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:798) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:228) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1358) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1204) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:882) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) ~[spring-boot-2.2.6.RELEASE.jar:2.2.6.RELEASE]
    at de.qedcon.moscowmule.MoscowMuleApplication.main(MoscowMuleApplication.java:25) ~[classes/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) ~[spring-boot-devtools-2.2.6.RELEASE.jar:2.2.6.RELEASE]
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'locationManagementServiceImpl' defined in file [D:\Development\qedcon\moscowmule\target\classes\de\qedcon\moscowmule\locationmanagement\service\LocationManagementServiceImpl.class]: Unsatisfied dependency expressed through constructor parameter 5; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userManagementServiceImpl' defined in file [D:\Development\qedcon\moscowmule\target\classes\de\qedcon\moscowmule\usermanagement\service\UserManagementServiceImpl.class]: Unsatisfied dependency expressed through constructor parameter 3; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'modelMapper' defined in de.qedcon.moscowmule.MoscowMuleApplication: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.modelmapper.ModelMapper]: Factory method 'modelMapper' threw exception; nested exception is org.modelmapper.ConfigurationException: ModelMapper configuration errors:

1) Failed to configure mappings

1 error
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:798) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:228) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1358) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1204) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1290) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1210) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:885) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:789) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    ... 24 common frames omitted
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userManagementServiceImpl' defined in file [D:\Development\qedcon\moscowmule\target\classes\de\qedcon\moscowmule\usermanagement\service\UserManagementServiceImpl.class]: Unsatisfied dependency expressed through constructor parameter 3; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'modelMapper' defined in de.qedcon.moscowmule.MoscowMuleApplication: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.modelmapper.ModelMapper]: Factory method 'modelMapper' threw exception; nested exception is org.modelmapper.ConfigurationException: ModelMapper configuration errors:

1) Failed to configure mappings

1 error
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:798) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:228) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1358) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1204) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1290) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1210) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:885) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:789) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    ... 38 common frames omitted
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'modelMapper' defined in de.qedcon.moscowmule.MoscowMuleApplication: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.modelmapper.ModelMapper]: Factory method 'modelMapper' threw exception; nested exception is org.modelmapper.ConfigurationException: ModelMapper configuration errors:

1) Failed to configure mappings

1 error
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:656) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:484) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1290) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1210) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:885) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:789) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    ... 52 common frames omitted
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.modelmapper.ModelMapper]: Factory method 'modelMapper' threw exception; nested exception is org.modelmapper.ConfigurationException: ModelMapper configuration errors:

1) Failed to configure mappings

1 error
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:651) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    ... 66 common frames omitted
Caused by: org.modelmapper.ConfigurationException: ModelMapper configuration errors:

1) Failed to configure mappings

1 error
    at org.modelmapper.internal.Errors.throwConfigurationExceptionIfErrorsExist(Errors.java:241) ~[modelmapper-2.3.0.jar:na]
    at org.modelmapper.internal.ExplicitMappingBuilder.build(ExplicitMappingBuilder.java:244) ~[modelmapper-2.3.0.jar:na]
    at org.modelmapper.internal.ExplicitMappingBuilder.build(ExplicitMappingBuilder.java:96) ~[modelmapper-2.3.0.jar:na]
    at org.modelmapper.internal.TypeMapImpl.addMappings(TypeMapImpl.java:92) ~[modelmapper-2.3.0.jar:na]
    at org.modelmapper.internal.TypeMapStore.getOrCreate(TypeMapStore.java:124) ~[modelmapper-2.3.0.jar:na]
    at org.modelmapper.ModelMapper.addMappings(ModelMapper.java:113) ~[modelmapper-2.3.0.jar:na]
    at de.qedcon.moscowmule.MoscowMuleApplication.modelMapper(MoscowMuleApplication.java:38) ~[classes/:na]
    at de.qedcon.moscowmule.MoscowMuleApplication$$EnhancerBySpringCGLIB$$1c0b08e7.CGLIB$modelMapper$0(<generated>) ~[classes/:na]
    at de.qedcon.moscowmule.MoscowMuleApplication$$EnhancerBySpringCGLIB$$1c0b08e7$$FastClassBySpringCGLIB$$8262a926.invoke(<generated>) ~[classes/:na]
    at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244) ~[spring-core-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:331) ~[spring-context-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    at de.qedcon.moscowmule.MoscowMuleApplication$$EnhancerBySpringCGLIB$$1c0b08e7.modelMapper(<generated>) ~[classes/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.2.5.RELEASE.jar:5.2.5.RELEASE]
    ... 67 common frames omitted
Caused by: java.lang.UnsupportedOperationException: null
    at org.modelmapper.internal.asm.ClassVisitor.visitNestHostExperimental(ClassVisitor.java:158) ~[modelmapper-2.3.0.jar:na]
    at org.modelmapper.internal.asm.ClassReader.accept(ClassReader.java:541) ~[modelmapper-2.3.0.jar:na]
    at org.modelmapper.internal.asm.ClassReader.accept(ClassReader.java:391) ~[modelmapper-2.3.0.jar:na]
    at org.modelmapper.internal.ExplicitMappingBuilder.visitPropertyMap(ExplicitMappingBuilder.java:259) ~[modelmapper-2.3.0.jar:na]
    at org.modelmapper.PropertyMap.configure(PropertyMap.java:386) ~[modelmapper-2.3.0.jar:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
    at org.modelmapper.internal.ExplicitMappingBuilder.build(ExplicitMappingBuilder.java:227) ~[modelmapper-2.3.0.jar:na]
    ... 82 common frames omitted

这里是完整的 ProjectConverter 类：

@Service
@Getter @RequiredArgsConstructor
public class ProjectConverter {
    
    
    public Converter<List<Location>, List<Long>> locationToLongConverter = new Converter<List<Location>, List<Long>>() {

        @Override
        public List<Long> convert(MappingContext<List<Location>, List<Long>> context) {
            List<Location> source = context.getSource();
            List<Long> destination = context.getDestination();
            
            for (Location location : source) {
                destination.add(location.getId());
            }
            
            return destination;
        }       
    
    };  
    
    PropertyMap<Project, ProjectDTO> itemDTOMap = new PropertyMap<Project, ProjectDTO>() {

        @Override
        protected void configure() {
            using(locationToLongConverter).map(Project::getLocations, ProjectDTO::setAssignedLocations);
        }
    };  

}

任何想法我做错了什么？

【问题讨论】：

能分享一下projectConverter类吗？
@Gurkanİlleez：我已附上。
引起：java.lang.UnsupportedOperationException: null at org.modelmapper.internal.asm.ClassVisitor.visitNestHostExperimental(ClassVisitor.java:158) ~[modelmapper-2.3.0.jar:na] ClassVisitor抛出 UnsupportedOperation
很可能是错误的 jar 版本

标签： java spring spring-boot dto modelmapper

【解决方案1】：

这是 ModelMapper 的一个 bug，在 2.3.2 或更高版本上修复：

UnsupportedOperationException when adding PropertyMap #404

另外，locationToLongConverter#convert()上的NPE问题应该修复了：

final List<Long> destination = new ArrayList<>();

顺便说一句，这段代码可以写得更简单：


    @Bean
    public ModelMapper modelMapper() {
        final Converter<List<Location>, List<Long>> locationConverter = ctx -> ctx.getSource().stream()
            .map(Location::getId).collect(Collectors.toList());

        final ModelMapper mapper = new ModelMapper();
        mapper.typeMap(Project.class, ProjectDTO.class)
            .addMappings(m -> {
                m.using(locationConverter).map(Project::getLocations, ProjectDTO::setAssignedLocations);
            });
        return mapper;
    }

（ProjectConverter.java 不是必需的。）

参考：

http://modelmapper.org/user-manual/property-mapping/

【讨论】：

【解决方案2】：

根据错误跟踪，它更像是名称为 locationManagementServiceImpl 的依赖项的问题，所以我猜你错过了一些东西，要么你忘记添加 @Service / @Componenet，因为该 bean 没有加载到 spring 上下文中或错过添加它依赖。

Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'locationManagementServiceImpl' defined in file [D:\Development\qedcon\moscowmule\target\classes\de\qedcon\moscowmule\locationmanagement\service\LocationManagementServiceImpl.class]: Unsatisfied dependency expressed through constructor parameter 5; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'userManagementServiceImpl' defined in file

【讨论】：

我认为这是因为我还在该服务中注入了 modelmapper bean。当我删除我的自定义映射“mapper.addMappings(projectConverter.getItemDTOMap());”应用程序启动顺利。
你在locationManagementServiceImpl 中注入了ModelMapper 吗？

【解决方案3】：

谢谢大家，我升级到modelmapper v2.3.8，现在可以正常工作了。

【讨论】：