差異處
這裏顯示兩個版本的差異處。
下次修改 | 前次修改 | ||
java:web:resteasy:fetch_raw_message [2018/07/01 19:33] tony 建立 |
java:web:resteasy:fetch_raw_message [2023/06/25 09:48] (目前版本) |
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{{tag>resteasy}} | {{tag>resteasy}} | ||
- | ====== How to fetch raw message after the request is failed? (working) ====== | + | ====== RESTEasy - How to fetch raw message after the request is failed? ====== |
===== Problem ===== | ===== Problem ===== | ||
- | RESTEasy jackson provider讓我們可以輕鬆的將第三方服務回應的json內容,轉成我們自己的物件,讓程式碼只專注於資源物件的操作;然而,第三方服務並非永遠都如你預期,它可能突然更新甚至吐出你不認得的訊息。我有幸遇到這樣的問題,也讓我思考著該如何將原始資料記錄下來以回報第三方服務提供者。本篇文章分享可能的作法,可依照你的需求自行挑選。 | + | RESTEasy jackson provider讓我們可以輕鬆的將第三方服務回應的json內容,轉成我們自己的物件,讓程式碼只專注於資源物件的操作;然而,第三方服務並非永遠都如你預期,它可能突然更新而吐出無法處理的訊息: |
+ | <code> | ||
+ | javax.ws.rs.ProcessingException: RESTEASY003145: Unable to find a MessageBodyReader of content-type text/html;charset=iso-8859-1 | ||
+ | </code> | ||
+ | 我有幸遇到這樣的問題,也讓我思考著該如何將原始資料記錄下來以回報第三方服務提供者。本篇文章分享可能的作法,可依照你的需求自行挑選。\\ | ||
+ | \\ | ||
+ | (完整程式內容可以從github上clone: [[https://github.com/frank007love/ResteasyPractice|link]]) | ||
+ | ===== How to resolve? ===== | ||
+ | ==== ReadInterceptor & InputStreamSniffer ==== | ||
+ | 一開始遇到這個問題時,我的想法是: 是否可以透過[[https://blog.wfyvv.com/blog/2018/03/jax-rs/|interceptor]]去處理? 我所提供的第一個方法,是註冊一個ReadInterceptor,並且wrap原始的InputStream,將讀取的內容給記錄下來。首先是ReaderInterceptor,它會從Context中取出InputStream,並將其wrap成InputStreamSniffer,待讀取流程執行後,就可以透過getReadContent去拿到讀取的內容: | ||
+ | <code java> | ||
+ | @Provider | ||
+ | public class SnifferReadInterceptor implements ReaderInterceptor { | ||
+ | private InputStreamSniffer inputStreamSniffer = null; | ||
+ | |||
+ | @Override | ||
+ | public Object aroundReadFrom(ReaderInterceptorContext context) throws IOException, WebApplicationException { | ||
+ | InputStream inputStream = context.getInputStream(); | ||
+ | |||
+ | inputStreamSniffer = new InputStreamSniffer(inputStream); | ||
+ | context.setInputStream(inputStreamSniffer); | ||
+ | |||
+ | return context.proceed(); | ||
+ | } | ||
+ | |||
+ | public String getReadContent(){ | ||
+ | return inputStreamSniffer.getContent(); | ||
+ | } | ||
+ | } | ||
+ | </code> | ||
+ | InputStreamSniffer則是將讀取的動作delegate給原始的InputStream,並悄悄地記下讀取內容: | ||
+ | <code java> | ||
+ | public class InputStreamSniffer extends InputStream { | ||
+ | |||
+ | private InputStream srcInputStream; | ||
+ | private StringBuilder contentStringBuilder; | ||
+ | |||
+ | public InputStreamSniffer(InputStream inputStream){ | ||
+ | srcInputStream = inputStream; | ||
+ | contentStringBuilder = new StringBuilder(); | ||
+ | } | ||
+ | |||
+ | @Override | ||
+ | public int read() throws IOException { | ||
+ | int read_c = srcInputStream.read(); | ||
+ | contentStringBuilder.append((char)read_c); | ||
+ | return read_c; | ||
+ | } | ||
+ | // .. skip | ||
+ | </code> | ||
+ | 我簡單的寫了一個測試,想要確認將message轉為json物件發生問題時,readInterceptor是否可以拿到message: | ||
+ | <code java> | ||
+ | @Test | ||
+ | public void testSnifferReadInterceptorWithReadFailed(){ | ||
+ | Invocation invocation = initInvocation(); | ||
+ | |||
+ | Response response = null; | ||
+ | try { | ||
+ | response = invocation.invoke(); | ||
+ | response.readEntity(TestModel.class); | ||
+ | fail("should be failed "); | ||
+ | } catch( ProcessingException e ) { | ||
+ | // Can't find valid messageBodyReader | ||
+ | assertTrue(readInterceptor.getReadContent().isEmpty()); | ||
+ | } finally { | ||
+ | response.close(); | ||
+ | } | ||
+ | } | ||
+ | </code> | ||
+ | 答案是不行,這是由於RESTEasy在讀取訊息前,會先根據Response Header中宣告的MediaType去找尋是否有對應的MessageBodyRead。 | ||
+ | ==== Read All Content of ReadInterceptor ==== | ||
+ | 由於我們無法於執行過程中解決這個問題,因此改在ReadInterceptor中,先將所有內容讀出來: | ||
+ | <code java> | ||
+ | public class DebugReadInterceptor implements ReaderInterceptor{ | ||
+ | |||
+ | private String content; | ||
+ | |||
+ | @Override | ||
+ | public Object aroundReadFrom(ReaderInterceptorContext context) throws IOException, WebApplicationException { | ||
+ | InputStream inputStream = context.getInputStream(); | ||
+ | content = IOUtils.toString(inputStream); | ||
+ | |||
+ | context.setInputStream(new ByteArrayInputStream(content.getBytes())); | ||
+ | return context.proceed(); | ||
+ | } | ||
+ | |||
+ | public String getContent(){ | ||
+ | return content; | ||
+ | } | ||
+ | } | ||
+ | </code> | ||
+ | 這個方法是可以解決目前遇到的問題,但缺點是每次請求都一定會多處理一次內容。於是我把腦筋動到了MessageBodyReader身上。 | ||
+ | ==== Customized MessageBodyReader ==== | ||
+ | 我新增一個名為CompositeMessageBodyProvider的類別,去implement MessageBodyReader;isReadable永遠回傳true,將搜尋合適MessageBodyReader動作交由readFrom處理,如果找不到就丟ProcessingException上去。Client可以攔截此例外決定要處理的方式: | ||
+ | <code java> | ||
+ | @Provider | ||
+ | @Consumes(MediaType.WILDCARD) | ||
+ | @Produces(MediaType.WILDCARD) | ||
+ | public class CompositeMessageBodyProvider implements MessageBodyReader<Object>, MessageBodyWriter<Object> { | ||
+ | |||
+ | private List<MessageBodyReader<Object>> messageBodyReaders = new ArrayList<>(); | ||
+ | |||
+ | @Override | ||
+ | public boolean isReadable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) { | ||
+ | return true; | ||
+ | } | ||
+ | |||
+ | private Optional<MessageBodyReader<Object>> findReader(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType){ | ||
+ | return messageBodyReaders.stream().filter(writter->writter.isReadable(type, genericType, annotations, mediaType)).findAny(); | ||
+ | } | ||
+ | |||
+ | @Override | ||
+ | public Object readFrom(Class<Object> type, Type genericType, Annotation[] annotations, MediaType mediaType, | ||
+ | MultivaluedMap<String, String> httpHeaders, InputStream entityStream) | ||
+ | throws IOException, WebApplicationException { | ||
+ | |||
+ | Optional<MessageBodyReader<Object>> reader = findReader(type, genericType, annotations, mediaType); | ||
+ | if(reader.isPresent()){ | ||
+ | return reader.get().readFrom(type, genericType, annotations, mediaType, httpHeaders, entityStream); | ||
+ | } | ||
+ | |||
+ | String output = IOUtils.toString(entityStream); | ||
+ | throw new ProcessingException("Unexpected content: " + output); | ||
+ | } | ||
+ | // .. skip | ||
+ | </code> | ||
+ | ===== Summary ===== | ||
+ | 以parse error、unexpected media type與unexpected json content(parse ok)三種錯誤來說: | ||
+ | - ReadInterceptor & InputStreamSniffer: 適用於parse error與unexpected json content。 | ||
+ | - Read All Content of ReadInterceptor: 適用於以上提及的所有錯誤情形,但效率較差。 | ||
+ | - Customized MessageBodyReader: 適用於unexpected media type。 | ||
+ | 要使用哪種方式,可仔細評估後再決定。 | ||
+ | ===== Reference ===== | ||
+ | - [[https://blog.wfyvv.com/blog/2018/03/jax-rs/|JAX-RS 2.0 简介及其过滤器与拦截器]] | ||
+ | - [[https://dennis-xlc.gitbooks.io/restful-java-with-jax-rs-2-0-en/cn/part1/chapter12/ordering_filters_and_interceptors.html|Ordering Filters and Interceptors]] | ||
+ | ===== ===== | ||
+ | ---- | ||
+ | \\ | ||
+ | ~~DISQUS~~ | ||