如何在 Spring 中使用 ModelMapper

Question

Cannot instantiate the type ModelMapper.

The method map(Product, Class<ProductDTO>) is undefined for the type ModelMapper.

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-01-20 12:59:36.344 ERROR 14280 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'productController': Unsatisfied dependency expressed through field 'modelMapper'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'modelMapper' defined in class path resource [com/example/demo/Config/Config.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [springfox.documentation.swagger2.mappers.ModelMapper]: Factory method 'modelMapper' threw exception; nested exception is java.lang.Error: Unresolved compilation problem: 
    Cannot instantiate the type ModelMapper
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:643) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1415) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:608) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:531) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:944) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:923) ~[spring-context-5.3.3.jar:5.3.3]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:588) ~[spring-context-5.3.3.jar:5.3.3]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:144) ~[spring-boot-2.4.2.jar:2.4.2]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:767) ~[spring-boot-2.4.2.jar:2.4.2]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759) ~[spring-boot-2.4.2.jar:2.4.2]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:426) ~[spring-boot-2.4.2.jar:2.4.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:326) ~[spring-boot-2.4.2.jar:2.4.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1311) ~[spring-boot-2.4.2.jar:2.4.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1300) ~[spring-boot-2.4.2.jar:2.4.2]
    at com.example.demo.ProductManagmentApplication.main(ProductManagmentApplication.java:10) ~[classes/:na]
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'modelMapper' defined in class path resource [com/example/demo/Config/Config.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [springfox.documentation.swagger2.mappers.ModelMapper]: Factory method 'modelMapper' threw exception; nested exception is java.lang.Error: Unresolved compilation problem: 
    Cannot instantiate the type ModelMapper

    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:658) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:486) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1336) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1179) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:571) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:531) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1380) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1300) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640) ~[spring-beans-5.3.3.jar:5.3.3]
    ... 20 common frames omitted
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [springfox.documentation.swagger2.mappers.ModelMapper]: Factory method 'modelMapper' threw exception; nested exception is java.lang.Error: Unresolved compilation problem: 
    Cannot instantiate the type ModelMapper

    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) ~[spring-beans-5.3.3.jar:5.3.3]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:653) ~[spring-beans-5.3.3.jar:5.3.3]
    ... 33 common frames omitted
Caused by: java.lang.Error: Unresolved compilation problem: 
    Cannot instantiate the type ModelMapper

Answer 1

它找不到bean，建议您创建一个Bean。所以你也不要违反 DRY（不要重复自己）等原则。

@Configuration
public class ModelMapperConfig {
    
    @Bean
    public ModelMapper modelMapper() {
        return new ModelMapper();
    }
    
}

有关更多信息，您可以查看 baeldung 页面： https://www.baeldung.com/entity-to-and-from-dto-for-a-java-spring-application