spring - 在 Spring MVC 中使用 Spring 的 DomainClassConverter 的问题

Question

我正在尝试在我的 Spring MVC 项目中使用 Spring 的 DomainClassConverter 功能。 (我只有非常基本的 Spring MVC 和 Spring 知识，对于这里的任何幼稚问题，请提前道歉)。

来自 API docs :

The DomainClassConverter allows you to use domain types in your Spring MVC controller 
method signatures directly, so that you don't have to manually lookup the instances via 
the repository: (PS: Example 1.20)

我从上面了解到的是，我不必编写 finder 方法，并且 Spring 提供了 User目的。所以这些是我做的步骤:

在 applicationcontext.xml 中包含以下 XML 行.

<bean class="org.springframework.data.web.config.SpringDataWebConfiguration" />
<bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
<property name="converters">
    <list>
        <bean class="com.rl.userservice.controller.UserConverter"/>
    </list>
</property>

在我的 pom.xml 中包含此依赖项每 Spring Data REST文档:

<dependencies>
    <dependency>
        <groupId>org.springframework.data</groupId>
        <artifactId>spring-data-rest-webmvc</artifactId>
        <version>2.0.0.BUILD-SNAPSHOT</version>
    </dependency>
</dependencies>

我的 Controller 如下所示:

@Controller
@RequestMapping(value = "/api/newuser")
public class NewUserServiceController {
      @Autowired
  NewUserRepository newUserRepository;

  @RequestMapping("/{id}")
    public String showUserForm(@PathVariable("id") NewUser newUser, Model model) {

      model.addAttribute("newUser", newUser);
      return "userForm";
    } 
}

存储库是这样的:

@Repository
public interface NewUserRepository extends JpaRepository<NewUser, Integer> {
}

这是我的转换器服务:

final class UserConverter implements Converter<Integer, NewUser> {
    NewUserRepository newUserRepository;

    public NewUser convert(Integer username) {
        return newUserRepository.findOne(username);
    } 
}

当我运行程序时 tomcat 启动成功，但是当访问 URL localhost:8080/userservice/api/newuser/1 时，我得到以下异常:

type Exception report
    message
    description The server encountered an internal error () that prevented it from fulfilling this request.
    exception
    org.springframework.beans.ConversionNotSupportedException: Failed to convert value of type 'java.lang.String' to required type
'com.mpp.userservice.domain.NewUser'; nested exception is
java.lang.IllegalStateException: Cannot convert value of type  
[java.lang.String] to required type
[com.mpp.userservice.domain.NewUser]: no matching editors or
conversion strategy found
      org.springframework.beans.TypeConverterSupport.doConvert(TypeConverterSupport.java:71)
      org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:45)
      org.springframework.validation.DataBinder.convertIfNecessary(DataBinder.java:595)
      org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:101)
      org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:77)
      org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:162)
      org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:123)
      org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
      org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
      org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
      org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
      org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
      org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
      org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
      org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
      javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
      org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
      javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

    root cause
    java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type
[com.mpp.userservice.domain.NewUser]: no matching editors or
conversion strategy found
      org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:264)
      org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:93)
      org.springframework.beans.TypeConverterSupport.doConvert(TypeConverterSupport.java:61)
      org.springframework.beans.TypeConverterSupport.convertIfNecessary(TypeConverterSupport.java:45)
      org.springframework.validation.DataBinder.convertIfNecessary(DataBinder.java:595)
      org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:101)
      org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:77)
      org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:162)
      org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:123)
      org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
      org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
      org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
      org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
      org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
      org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
      org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
      org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
      javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
      org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
      javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

    note The full stack trace of the root cause is available in the Apache Tomcat/6.0.29 logs.
    mpp.

虽然不是最好的代码，但这是我的 Controller :

public @ResponseBody ResponseEntity<ModelMap> getUserTypeJSON(@PathVariable("userID" String userID, HttpServletResponse response)  { 
    UserType UserType = UserTypeRepository.findOne(id);
    model.addAttribute("Name",UserType.getName());  
    ...
} 

有一个例子 here我引用了，但这是使用自定义转换器，但似乎没有使用域转换器服务。请指教。如果我想减少编写 CRUD 操作的样板代码，这是要走的路吗？这样做的真正好处是什么 DomainClassConverter我什么时候可以用另一种方式获取数据？

根据 Oliver Gierke 建议更新 - 仍然无效，同样的错误

该文件描述了:

<mvc:annotation-driven conversion-service="conversionService" />
<bean class="org.springframework.data.repository.support.DomainClassConverter">
  <constructor-arg ref="conversionService" />
</bean>

所以我更新了我的 applicationcontext.xml如下，但同样的问题:

    <mvc:annotation-driven conversion-service="conversionService"/>

  <bean class="org.springframework.data.repository.support.DomainClassConverter">
    <constructor-arg ref="conversionService" />
  </bean>

    <bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
    <property name="converters">
        <list>
          <bean class="com.rl.userservice.controller.UserConverter"/>
        </list>
    </property>
  </bean>

还是一样的问题。

更新: DomainClassConverter 与 Java Config 一起工作，但不是 XML 方式(至少尝试了这里和互联网上其他地方建议的许多组合)。仅适用于可能感兴趣并获得一些有用信息的其他人，这里是使用的代码。

pom.xml(可能需要清理)

<dependency>
    <groupId>org.springframework.data</groupId>
    <artifactId>spring-data-rest-webmvc</artifactId>
    <version>2.0.0.M1</version>
</dependency>

<dependency>
    <groupId>org.springframework.data</groupId>
    <artifactId>spring-data-jpa</artifactId>
    <version>1.4.3.RELEASE</version>
</dependency>

Controller 文件(可能需要清理)

@RequestMapping("/domain/{id}")
  public @ResponseBody ResponseEntity<ModelMap> showDomainUserForm(@PathVariable("id") User userMatch, HttpServletResponse response) {

  // some code omitted…  

    ModelMap model = new ModelMap();        
    model.addAttribute("DOMAIN-MAP","Domain Controller Service");
    model.addAttribute("Name",userMatch.getName());
    model.addAttribute("Phone",userMatch.getPhone());                                           

    // some code omitted…


  } 

使用来自 resource1 的示例组装的 Java 配置文件和 resource2 .
(可能需要清理)

package com.rl.userservice.controller;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.repository.support.DomainClassConverter;
import org.springframework.format.support.FormattingConversionService;
import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;

@Configuration
@ComponentScan
@EnableWebMvc
public class WebConfig extends WebMvcConfigurationSupport{
     @Bean
     public RequestMappingHandlerMapping requestMappingHandlerMapping() {
      RequestMappingHandlerMapping handlerMapping = super.requestMappingHandlerMapping();
      handlerMapping.setUseSuffixPatternMatch(false);
      handlerMapping.setUseTrailingSlashMatch(false);
      return handlerMapping;
     } 


     @Bean
     public DomainClassConverter<?> domainClassConverter() {
         return new DomainClassConverter<FormattingConversionService>(mvcConversionService());
     }

     @Override
     public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
         configurer.enable();
     }

}

在 applicationContext.xml 中添加以下 bean 定义

<bean class="com.rl.userservice.controller.WebConfig"/>

Answer 1

URL 是 String , 所以 {id}是 String也。因此，您的服务必须能够转换 String至 NewUser ，不是 Integer就像你的一样。