不幸的是，所有Spring Data JPA / Rest最高版本为2.1.0.RELEASE都无法立即满足你的需求。该源代码隐藏在Spring Data Commons / JPA本身中。Spring Data JPA仅支持Id和EmbeddedId作为标识符。
摘录JpaPersistentPropertyImpl：
static {
// [...]
annotations = new HashSet<Class<? extends Annotation>>();
annotations.add(Id.class);
annotations.add(EmbeddedId.class);
ID_ANNOTATIONS = annotations;
}
Spring Data Commons不支持组合属性的概念。它彼此独立地对待一个类的每个属性。
当然，你可以修改Spring Data Rest。但这很麻烦，不能从根本上解决问题，并且降低了框架的灵活性。
在你的配置中覆盖repositoryExporterHandlerAdapter并返回CustomPersistentEntityResourceAssemblerArgumentResolver。此外，覆盖backendIdConverterRegistry并添加CustomBackendIdConverter到已知列表id converter：
import org.springframework.beans.factory.Listablebeanfactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.data.rest.core.projection.ProxyProjectionFactory;
import org.springframework.data.rest.webmvc.RepositoryRestHandlerAdapter;
import org.springframework.data.rest.webmvc.config.RepositoryRestMvcConfiguration;
import org.springframework.data.rest.webmvc.spi.BackendIdConverter;
import org.springframework.data.rest.webmvc.support.HttpMethodHandlerMethodArgumentResolver;
import org.springframework.data.web.config.EnableSpringDataWebSupport;
import org.springframework.hateoas.ResourceProcessor;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.plugin.core.OrderAwarePluginRegistry;
import org.springframework.plugin.core.PluginRegistry;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
@Configuration
@Import(RepositoryRestMvcConfiguration.class)
@EnableSpringDataWebSupport
public class RestConfig extends RepositoryRestMvcConfiguration {
@Autowired(required = false) List<ResourceProcessor<?>> resourceProcessors = Collections.emptyList();
@Autowired
Listablebeanfactory beanfactory;
@Override
@Bean
public PluginRegistry<BackendIdConverter, Class<?>> backendIdConverterRegistry() {
List<BackendIdConverter> converters = new ArrayList<BackendIdConverter>(3);
converters.add(new CustomBackendIdConverter());
converters.add(BackendIdConverter.DefaultIdConverter.INSTANCE);
return OrderAwarePluginRegistry.create(converters);
}
@Bean
public RequestMappingHandlerAdapter repositoryExporterHandlerAdapter() {
List<HttpMessageConverter<?>> messageConverters = defaultMessageConverters();
configureHttpMessageConverters(messageConverters);
RepositoryRestHandlerAdapter handlerAdapter = new RepositoryRestHandlerAdapter(defaultMethodArgumentResolvers(),
resourceProcessors);
handlerAdapter.setMessageConverters(messageConverters);
return handlerAdapter;
}
private List<HandlerMethodArgumentResolver> defaultMethodArgumentResolvers()
{
CustomPersistentEntityResourceAssemblerArgumentResolver peraResolver = new CustomPersistentEntityResourceAssemblerArgumentResolver(
repositories(), entityLinks(), config().projectionConfiguration(), new ProxyProjectionFactory(beanfactory));
return Arrays.asList(pageableResolver(), sortResolver(), serverHttpRequestMethodArgumentResolver(),
repoRequestArgumentResolver(), persistentEntityArgumentResolver(),
resourceMetadataHandlerMethodArgumentResolver(), HttpMethodHandlerMethodArgumentResolver.INSTANCE,
peraResolver, backendIdHandlerMethodArgumentResolver());
}
}
创建CustomBackendIdConverter。此类负责呈现你的自定义实体ID：
import org.springframework.data.rest.webmvc.spi.BackendIdConverter;
import java.io.Serializable;
public class CustomBackendIdConverter implements BackendIdConverter {
@Override
public Serializable fromRequestId(String id, Class<?> entityType) {
return id;
}
@Override
public String toRequestId(Serializable id, Class<?> entityType) {
if(entityType.equals(Customer.class)) {
Customer c = (Customer) id;
return c.getId() + "_" +c.getStartVersion();
}
return id.toString();
}
@Override
public boolean supports(Class<?> delimiter) {
return true;
}
}
CustomPersistentEntityResourceAssemblerArgumentResolver反过来应该返回一个CustomPersistentEntityResourceAssembler：
import org.springframework.core.MethodParameter;
import org.springframework.data.repository.support.Repositories;
import org.springframework.data.rest.core.projection.ProjectionDeFinitions;
import org.springframework.data.rest.core.projection.ProjectionFactory;
import org.springframework.data.rest.webmvc.PersistentEntityResourceAssembler;
import org.springframework.data.rest.webmvc.config.PersistentEntityResourceAssemblerArgumentResolver;
import org.springframework.data.rest.webmvc.support.PersistentEntityProjector;
import org.springframework.hateoas.EntityLinks;
import org.springframework.web.bind.support.WebDataBinderFactory;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.support.ModelAndViewContainer;
public class CustomPersistentEntityResourceAssemblerArgumentResolver extends PersistentEntityResourceAssemblerArgumentResolver {
private final Repositories repositories;
private final EntityLinks entityLinks;
private final ProjectionDeFinitions projectionDeFinitions;
private final ProjectionFactory projectionFactory;
public CustomPersistentEntityResourceAssemblerArgumentResolver(Repositories repositories, EntityLinks entityLinks,
ProjectionDeFinitions projectionDeFinitions, ProjectionFactory projectionFactory) {
super(repositories, entityLinks,projectionDeFinitions,projectionFactory);
this.repositories = repositories;
this.entityLinks = entityLinks;
this.projectionDeFinitions = projectionDeFinitions;
this.projectionFactory = projectionFactory;
}
public boolean supportsParameter(MethodParameter parameter) {
return PersistentEntityResourceAssembler.class.isAssignableFrom(parameter.getParameterType());
}
public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
String projectionParameter = webRequest.getParameter(projectionDeFinitions.getParameterName());
PersistentEntityProjector projector = new PersistentEntityProjector(projectionDeFinitions, projectionFactory,
projectionParameter);
return new CustomPersistentEntityResourceAssembler(repositories, entityLinks, projector);
}
}
CustomPersistentEntityResourceAssembler需要覆盖getSelfLinkFor。如你所见，entity.getIdproperty()返回Customer类的id或startVersion属性，而该属性又被用于借助来检索实际值BeanWrapper。在这里，我们使用instanceof运算符将整个框架短路。因此，你的Customer班级应实施Serializable进一步处理。
import org.springframework.data.mapping.PersistentEntity;
import org.springframework.data.mapping.model.BeanWrapper;
import org.springframework.data.repository.support.Repositories;
import org.springframework.data.rest.webmvc.PersistentEntityResourceAssembler;
import org.springframework.data.rest.webmvc.support.Projector;
import org.springframework.hateoas.EntityLinks;
import org.springframework.hateoas.Link;
import org.springframework.util.Assert;
public class CustomPersistentEntityResourceAssembler extends PersistentEntityResourceAssembler {
private final Repositories repositories;
private final EntityLinks entityLinks;
public CustomPersistentEntityResourceAssembler(Repositories repositories, EntityLinks entityLinks, Projector projector) {
super(repositories, entityLinks, projector);
this.repositories = repositories;
this.entityLinks = entityLinks;
}
public Link getSelfLinkFor(Object instance) {
Assert.notNull(instance, "Domain object must not be null!");
Class<? extends Object> instanceType = instance.getClass();
PersistentEntity<?, ?> entity = repositories.getPersistentEntity(instanceType);
if (entity == null) {
throw new IllegalArgumentException(String.format("Cannot create self link for %s! No persistent entity found!",
instanceType));
}
Object id;
//this is a hack for demonstration purpose. don't do this at home!
if(instance instanceof Customer) {
id = instance;
} else {
BeanWrapper<Object> wrapper = BeanWrapper.create(instance, null);
id = wrapper.getProperty(entity.getIdproperty());
}
Link resourceLink = entityLinks.linkToSingleResource(entity.getType(), id);
return new Link(resourceLink.getHref(), Link.REL_SELF);
}
}
而已！你应该看到以下URI：
{
"_embedded" : {
"customers" : [ {
"name" : "test",
"_links" : {
"self" : {
"href" : "http://localhost:8080/demo/customers/1_1"
}
}
} ]
}
}
恕我直言，如果你正在从事绿色项目，我建议你IdClass完全放弃并使用基于Long类的技术简单ID。这已通过Spring Data Rest 2.1.0.RELEASE，Spring data JPA 1.6.0.RELEASE和Spring Framework 4.0.3RELEASE进行了测试。
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