英文:
Reproducing Spring Data Rest search controllers in Spring Boot 2.3
问题
直到Spring Boot 2.0版本，我可以复现由mongodb仓库暴露的查询方法生成的控制器。以下是一个示例代码：
领域实体
@Document(collection = "foos")
public class Foo {
@Id
private String id;
private String name;
// getters/setters omitted
}
Mongo仓库
public interface FooRepository extends MongoRepository<Foo, String> {
public Page<Foo> findByName(@Param("name") String name, Pageable pageable);
}
Spring Boot会自动通过/foos/search/findByName?name=...暴露搜索方法，并返回类似以下结果：
{
"_embedded" : {
"foos" : [ {
"name" : "qc",
"_links" : {
"self" : {
"href" : "http://localhost:8080/foos/56a8a8d5daffd28c9c907974"
},
"foo" : {
"href" : "http://localhost:8080/foos/56a8a8d5daffd28c9c907974"
}
}
} ]
},
"_links" : {
"self" : {
"href" : "http://localhost:8080/foos/search/findByName?name=qc&page=0&size=20"
}
},
"page" : {
"size" : 20,
"totalElements" : 1,
"totalPages" : 1,
"number" : 0
}
}
我可以使用以下自定义控制器和配置来复制它：
@RestController
@RequestMapping("foos")
@RequiredArgsConstructor // lombok
public class FooQueryController {
private final FooRepository repository;
private final PagedResourcesAssembler pagedResourcesAssembler;
@GetMapping(value = "search/query",
produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
public ResponseEntity custom(@RequestParam("name") String name,
Pageable pageable,
PersistentEntityResourceAssembler resourceAssembler) {
var page = repository.findByName(name, pageable);
var model = pagedResourcesAssembler.toResource(page, resourceAssembler);
return ResponseEntity.ok(model);
}
}
// 启用在RestController中注入PersistentEntityResourceAssembler，参见https://jira.spring.io/browse/DATAREST-657获取详细信息
@Configuration
@Order(Ordered.HIGHEST_PRECEDENCE)
@RequiredArgsConstructor
public class MvcConfiguration implements WebMvcConfigurer {
// 警告：不要更改此成员的名称 - 它将被RequestMappingHandlerAdapter$repositoryExporterHandlerAdapter()注入。
private final RequestMappingHandlerAdapter repositoryExporterHandlerAdapter;
@Override
public void addArgumentResolvers(
List<HandlerMethodArgumentResolver> argumentResolvers) {
List<HandlerMethodArgumentResolver> customArgumentResolvers =
repositoryExporterHandlerAdapter.getCustomArgumentResolvers();
argumentResolvers.addAll(customArgumentResolvers);
}
}
有了这个，我可以向/foos/search/query?name=...发送请求，并获得预期的响应：
{
"_embedded" : {
"foos" : [ {
"name" : "qc",
"_links" : {
"self" : {
"href" : "http://localhost:8080/foos/56a8a8d5daffd28c9c907974"
},
"foo" : {
"href" : "http://localhost:8080/foos/56a8a8d5daffd28c9c907974"
}
}
} ]
},
"_links" : {
"self" : {
"href" : "http://localhost:8080/foos/search/query?name=qc&page=0&size=20"
}
},
"page" : {
"size" : 20,
"totalElements" : 1,
"totalPages" : 1,
"number" : 0
}
}
切换到Spring Boot 2.3，并在控制器中使用Spring HATEOAS 1.0 API：
@RestController
@RequestMapping("foos")
@RequiredArgsConstructor
public class FooQueryController {
private final FooRepository repository;
private final PagedResourcesAssembler pagedResourcesAssembler;
@GetMapping(value = "search/query",
produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity custom(@RequestParam("name") String name,
Pageable pageable,
PersistentEntityResourceAssembler resourceAssembler) {
var page = repository.findByName(name, pageable);
var model = pagedResourcesAssembler.toModel(page, resourceAssembler);
return ResponseEntity.ok(model);
}
}
现在我会得到以下结果：
{"_embedded":{"foos":[{"id":"56a8a8d5daffd28c9c907974","name":"qc","embeddeds":{},"nested":false,"persistentEntity":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{
一下的日志中会出现以下错误：
```text
2020-08-06 18:11:20.968 WARN 9932 --- [nio-8080-exec-1] .w.s.m.s.DefaultHandlerExceptionResolver : Failure while trying to resolve exception [org.springframework.http.converter.HttpMessageNotWritableException]
java.lang.IllegalStateException: Cannot call sendError() after the response has been committed
at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:472) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver.sendServerError(DefaultHandlerExceptionResolver.java:550) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver.handleHttpMessageNotWritable(DefaultHandlerExceptionResolver.java:440) ~[spring-webmvc-5.
<details>
<summary>英文:</summary>
Until Spring Boot 2.0, I could reproduce the controllers generated for query methods exposed by a mongodb repository.
Here is a code sample:
Domain Entity
@Document(collection = "foos")
public class Foo {
@Id
private String id;
private String name;
// getters/setters omitted
}
Mongo repository
public interface FooRepository extends MongoRepository<Foo, String> {
public Page<Foo> findByName(@Param("name") String name, Pageable pageable);
}
Spring Boot automatically exposes the search method through `/foos/search/findByName?name=...` with a result similar to this:
{
"_embedded" : {
"foos" : [ {
"name" : "qc",
"_links" : {
"self" : {
"href" : "http://localhost:8080/foos/56a8a8d5daffd28c9c907974"
},
"foo" : {
"href" : "http://localhost:8080/foos/56a8a8d5daffd28c9c907974"
}
}
} ]
},
"_links" : {
"self" : {
"href" : "http://localhost:8080/foos/search/findByName?name=qc&page=0&size=20"
}
},
"page" : {
"size" : 20,
"totalElements" : 1,
"totalPages" : 1,
"number" : 0
}
}
I could reproduce it with the following custom controller and configuration
@RestController
@RequestMapping("foos")
@RequiredArgsConstructor // lombok
public class FooQueryController {
private final FooRepository repository;
private final PagedResourcesAssembler pagedResourcesAssembler;
@GetMapping(value = "search/query",
produces = MediaType.APPLICATION_JSON_UT8_VALUE)
public ResponseEntity custom(@RequestParam("name") String name,
Pageable pageable,
PersistentEntityResourceAssembler resourceAssembler) {
var page = repository.findByName(name, pageable);
var model = pagedResourcesAssembler.toResource(page, resourceAssembler);
return ResponseEntity.ok(model);
}
}
// Enables injecting a PersistentEntityResourceAssembler in a RestController
// see https://jira.spring.io/browse/DATAREST-657 for details
@Configuration
@Order(Ordered.HIGHEST_PRECEDENCE)
@RequiredArgsConstructor
public class MvcConfiguration implements WebMvcConfigurer {
// WARNING: do NOT change the name of this member - it is injected with the
// RequestMappingHandlerAdapter$repositoryExporterHandlerAdapter().
private final RequestMappingHandlerAdapter repositoryExporterHandlerAdapter;
@Override
public void addArgumentResolvers(
List<HandlerMethodArgumentResolver> argumentResolvers) {
List<HandlerMethodArgumentResolver> customArgumentResolvers =
repositoryExporterHandlerAdapter.getCustomArgumentResolvers();
argumentResolvers.addAll(customArgumentResolvers);
}
}
With this I can send a request to `/foos/search/query?name=...` and get the expected response:
{
"_embedded" : {
"foos" : [ {
"name" : "qc",
"_links" : {
"self" : {
"href" : "http://localhost:8080/foos/56a8a8d5daffd28c9c907974"
},
"foo" : {
"href" : "http://localhost:8080/foos/56a8a8d5daffd28c9c907974"
}
}
} ]
},
"_links" : {
"self" : {
"href" : "http://localhost:8080/foos/search/query?name=qc&page=0&size=20"
}
},
"page" : {
"size" : 20,
"totalElements" : 1,
"totalPages" : 1,
"number" : 0
}
}
Switching to Spring Boot 2.3, using the Spring HATEOAS 1.0 API in the controller
@RestController
@RequestMapping("foos")
@RequiredArgsConstructor
public class FooQueryController {
private final FooRepository repository;
private final PagedResourcesAssembler pagedResourcesAssembler;
@GetMapping(value = "search/query",
produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity custom(@RequestParam("name") String name,
Pageable pageable,
PersistentEntityResourceAssembler resourceAssembler) {
var page = repository.findByName(name, pageable);
var model = pagedResourcesAssembler.toModel(page, resourceAssembler);
return ResponseEntity.ok(model);
}
}
I now get the following result:
{"_embedded":{"foos":[{"id":"56a8a8d5daffd28c9c907974","name":"qc","embeddeds":{},"nested":false,"persistentEntity":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":{"name":"id","rawType":"java.lang.String","association":false,"owner":{"idProperty":
With the following errors in Spring's log:
2020-08-06 18:11:20.968 WARN 9932 --- [nio-8080-exec-1] .w.s.m.s.DefaultHandlerExceptionResolver : Failure while trying to resolve exception [org.springframework.http.converter.HttpMessageNotWritableException]
java.lang.IllegalStateException: Cannot call sendError() after the response has been committed
at org.apache.catalina.connector.ResponseFacade.sendError(ResponseFacade.java:472) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver.sendServerError(DefaultHandlerExceptionResolver.java:550) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver.handleHttpMessageNotWritable(DefaultHandlerExceptionResolver.java:440) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver.doResolveException(DefaultHandlerExceptionResolver.java:210) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:141) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.handler.HandlerExceptionResolverComposite.resolveException(HandlerExceptionResolverComposite.java:80) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.processHandlerException(DispatcherServlet.java:1300) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1111) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:626) ~[tomcat-embed-core-9.0.37.jar:4.0.FR]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) ~[tomcat-embed-core-9.0.37.jar:4.0.FR]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.37.jar:9.0.37]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1589) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) ~[na:na]
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) ~[na:na]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.37.jar:9.0.37]
at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]
2020-08-06 18:11:20.979 ERROR 9932 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Infinite recursion (StackOverflowError); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion (StackOverflowError) (through reference chain: org.springframework.data.mongodb.core.mapping.CachingMongoPersistentProperty["owner"]->org.springframework.data.mongodb.core.mapping.BasicMongoPersistentEntity["idProperty"]->org.springframework.data.mongodb.core.mapping.CachingMongoPersistentProperty["owner"]->org.springframework.data.mongodb.core.mapping.BasicMongoPersistentEntity["idProperty"]->org.springframework.data.mongodb.core.mapping.CachingMongoPersistentProperty["owner"]->org.springframework.data.mongodb.core.mapping.BasicMongoPersistentEntity["idProperty"]->org.springframework.data.mongodb.core.mapping.CachingMongoPersistentProperty["owner"]->org.springframework.data.mongodb.core.mapping.BasicMongoPersistentEntity["idProperty"]->org.springframework.data.mongodb.core.mapping.CachingMongoPersistentProperty["owner"]->org.springframework.data.mongodb.core.mapping.BasicMongoPersistentEntity["idProperty"]-> ... IT GOES ON AND ON LIKE THIS ... ->org.springframework.data.mongodb.core.mapping.BasicMongoPersistentEntity["idProperty"])] with root cause
java.lang.StackOverflowError: null
at java.base/java.lang.ClassLoader.defineClass1(Native Method) ~[na:na]
at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1016) ~[na:na]
at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:174) ~[na:na]
at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:800) ~[na:na]
at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:698) ~[na:na]
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:621) ~[na:na]
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:579) ~[na:na]
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178) ~[na:na]
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521) ~[na:na]
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:773) ~[jackson-databind-2.11.1.jar:2.11.1]
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:178) ~[jackson-databind-2.11.1.jar:2.11.1]
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:728) ~[jackson-databind-2.11.1.jar:2.11.1]
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:755) ~[jackson-databind-2.11.1.jar:2.11.1]
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:178) ~[jackson-databind-2.11.1.jar:2.11.1]
... IT GOES ON LIKE THIS FOR DOZENS AND DOZENS OF LINE
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:728) ~[jackson-databind-2.11.1.jar:2.11.1]
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:755) ~[jackson-databind-2.11.1.jar:2.11.1]
2020-08-06 18:11:21.553 ERROR 9932 --- [nio-8080-exec-1] s.e.ErrorMvcAutoConfiguration$StaticView : Cannot render error page for request [/foos/search/query] and exception [] as the response has already been committed. As a result, the response may have the wrong status code.
If if return the contents of `var page = repository.findByName(name, pageable);` instead of `var model = pagedResourcesAssembler.toModel(page, resourceAssembler);`, I get the following result:
{"content":[{"id":"56a8a8d5daffd28c9c907974","name":"qc"}],"pageable":{"sort":{"sorted":false,"unsorted":true,"empty":true},"offset":0,"pageNumber":0,"pageSize":20,"paged":true,"unpaged":false},"last":true,"totalPages":1,"totalElements":1,"size":20,"number":0,"sort":{"sorted":false,"unsorted":true,"empty":true},"numberOfElements":1,"first":true,"empty":false}
So the circular mess comes from the serialization `pagedResourcesAssembler.toModel(page, resourceAssembler)` (and probably the WebMvcConfigurer override).
</details>
# 答案1
**得分**: 2
我遇到了相同的`StackOverflowError: null`问题，当我调用`PersistentEntityResourceAssembler.toModel(Object)`时。我的代码返回的是一个`EntityModel`而不是`PagedModel`。我的问题是通过切换到`PersistentEntityResourceAssembler.toFullResource(Object)`来解决的。
`toModel(Object)`使用摘要投影，而`toFullResource(Object)`则不使用。我没有时间深入代码来查看是什么导致了无限循环引起栈溢出。
查看`PagedResourcesAssembler`的源代码，`PagedResourcesAssembler.toModel(Page, RepresentationModelAssembler)`调用了`RepresentationModelAssembler.toModel(Object)`。
因此，解决方法1是复制`PagedResourcesAssembler.toModel(Page, RepresentationModelAssembler)`的源代码，并使用`RepresentationModelAssembler.toFullResource(Object)`。
解决方法2是扩展`PagedResourcesAssembler`并重写`createModel(...)`方法。
在制定解决方法之前，我有一个问题。为什么要将`PersistentEntityResourceAssembler`传递给`PagedResourcesAssembler`？我的代码使用`PersistentEntityResourceAssembler`在我的自定义控制器返回单一资源时添加HTTP头`ETag`和`Last-Modified`。在构建集合资源（分页资源）的响应时使用`PersistentEntityResourceAssembler`有什么好处？
<details>
<summary>英文:</summary>
I had the same `StackOverflowError: null` when I call `PersistentEntityResourceAssembler.toModel(Object)`. My code returns a single `EntityModel` instead of a `PagedModel`. My problem is solved by switching to `PersistentEntityResourceAssembler.toFullResource(Object)`.
The `toModel(Object)` uses excerpt projection while `toFullResource(Object)` does not. I don't have time to dig into the code to check what produces an infinite loop to cause stack overflow.
Look at the source code of `PagedResourcesAssembler`, `PagedResourcesAssembler.toModel(Page, RepresentationModelAssembler)` calls `RepresentationModelAssember.toModel(Object)`.
So workaround 1 is copying the source code of `PagedResourcesAssembler.toModel(Page, RepresentationModelAssembler)` and use `RepresentationModelAssember.toFullResource(Object)`.
Workaround 2 is extending the `PagedResourcesAssembler` and overriding the `createModel(...)` method.
Before making the workaround, I have one question. Why do you pass a `PersistentEntityResourceAssembler` to `PagedResourcesAssembler`? My code uses `PersistentEntityResourceAssembler` to add HTTP headers `ETag` and `Last-Modified` when my custom controller returns a single resource. What good does it have to use `PersistentEntityResourceAssembler` to build the response of a collection resource (paged resource)?
</details>
# 答案2
**得分**: 0
由于 [Spring JIRA 上的此帖子](https://jira.spring.io/browse/DATAREST-838?focusedCommentId=154076&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-154076) 的帮助，我能够实现以下功能：
- 将控制器中的 `MultiValueMap` 参数转换为 `Predicate`
- 使用 `RepositoryRestController` 而不是 `RestController`，即能够将 `PersistentEntityResourceAssembler` 注入到控制器方法中。
根据接受的答案建议，自定义模型和模型装配器是不必要的。
配置一个 `QuerydslPredicateBuilder` bean：
```java
@Configuration
@RequiredArgsConstructor
public class QueryDslConfiguration {
private final ConversionService mvcConversionService;
private final QuerydslBindingsFactory querydslBindingsFactory;
@Bean
public QuerydslPredicateBuilder querydslPredicateBuilder() {
return new QuerydslPredicateBuilder(mvcConversionService, querydslBindingsFactory.getEntityPathResolver());
}
}
一个用于将 MultiValueMap 转换为 Predicate 的服务：
@Service
@RequiredArgsConstructor(onConstructor = @__(@Autowired))
public class PredicateService {
private final QuerydslPredicateBuilder querydslPredicateBuilder;
private final QuerydslBindingsFactory querydslBindingsFactory;
public <T> Predicate getPredicateFromParameters(final MultiValueMap<String, String> parameters, Class<T> tClass) {
TypeInformation<T> typeInformation = ClassTypeInformation.from(tClass);
return querydslPredicateBuilder.getPredicate(typeInformation,
parameters,
querydslBindingsFactory.createBindingsFor(typeInformation));
}
}
在控制器中使用这个转换器：
@RepositoryRestController
@RequiredArgsConstructor
public class FooController {
private final FooRepository repository;
private final PredicateService predicateService;
@GetMapping("/foos/search/query")
public PagedModel<Foo> query(
@RequestParam MultiValueMap<String, String> parameters,
Pageable pageable,
PersistentEntityResourceAssembler resourceAssembler) {
Predicate predicate = predicateService.getPredicateFromParameters(parameters, Foo.class);
Page<Foo> page = repository.findAll(predicate, pageable);
return pagedResourcesAssembler.toModel(page, resourceAssembler);
}
}
英文:
Thanks to this thread on Spring JIRA, I was able to:
- convert the controller
MultiValueMapparameters to aPredicate - use a
RepositoryRestControllerinstead of aRestController, ie be able to inject aPersistentEntityResourceAssemblerinto the controller method.
Custom models and models assembler, as suggested in the accepted answer, are not necessary.
Configure a QuerydslPredicateBuilder bean:
@Configuration
@RequiredArgsConstructor
public class QueryDslConfiguration {
private final ConversionService mvcConversionService;
private final QuerydslBindingsFactory querydslBindingsFactory;
@Bean
public QuerydslPredicateBuilder querydslPredicateBuilder() {
return new QuerydslPredicateBuilder(mvcConversionService, querydslBindingsFactory.getEntityPathResolver());
}
}
A service to convert a MultiValueMap to a Predicate:
@Service
@RequiredArgsConstructor(onConstructor = @__(@Autowired))
public class PredicateService {
private final QuerydslPredicateBuilder querydslPredicateBuilder;
private final QuerydslBindingsFactory querydslBindingsFactory;
public <T> Predicate getPredicateFromParameters(final MultiValueMap<String, String> parameters, Class<T> tClass) {
TypeInformation<T> typeInformation = ClassTypeInformation.from(tClass);
return querydslPredicateBuilder.getPredicate(typeInformation,
parameters,
querydslBindingsFactory.createBindingsFor(typeInformation));
}
}
Use the converter in a controller:
@RepositoryRestController
@RequiredArgsConstructor
public class FooController {
private final FooRepository repository;
private final PredicateService predicateService;
@GetMapping("/foos/search/query")
public PagedModel<Foo> query(
@RequestParam MultiValueMap<String, String> parameters,
Pageable pageable,
PersistentEntityResourceAssembler resourceAssembler) {
Predicate predicate = predicateService.getPredicateFromParameters(parameters, Foo.class);
Page<Parameter> page = repository.findAll(predicate,
return pagedResourcesAssembler.toModel(page, resourceAssembler);
}
}
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