我应该如何在RESTful JAX-RS Web服务中记录未捕获的异常？ [英] How should I log uncaught exceptions in my RESTful JAX-RS web service?
问题描述
我使用Jersey和Jackson在Glassfish 3.1.2下运行RESTful Web服务：
I have a RESTful web service running under Glassfish 3.1.2 using Jersey and Jackson:
@Stateless
@LocalBean
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
@Path("users")
public class UserRestService {
private static final Logger log = ...;
@GET
@Path("{userId:[0-9]+}")
public User getUser(@PathParam("userId") Long userId) {
User user;
user = loadUserByIdAndThrowApplicableWebApplicationExceptionIfNotFound(userId);
return user;
}
}
对于预期的例外情况，我抛出相应的 WebApplicationException ，我对发生意外异常时返回的HTTP 500状态感到满意。
For expected exceptions, I throw the appropriate WebApplicationException, and I'm happy with the HTTP 500 status that is returned if an unexpected exception occurs.
我现在想为这些意外异常添加日志记录，但是尽管搜索，但无法知道我应该如何进行此操作。
I would now like to add logging for these unexpected exceptions, but despite searching, cannot find out how I should be going about this.
我尝试过使用 Thread.UncaughtExceptionHandler 并且可以确认它是在方法体内应用的，但是从不调用它的 uncaughtException 方法，因为其他东西在它们到达我的处理程序之前处理未捕获的异常。
I have tried using a Thread.UncaughtExceptionHandler and can confirm that it is applied inside the method body, but its uncaughtException method is never called, as something else is handling the uncaught exceptions before they reach my handler.
我见过一些人使用的另一种选择是 ExceptionMapper ，它捕获所有异常，然后过滤掉WebApplicationExceptions：
Another option I've seen some people use is an ExceptionMapper, which catches all exceptions and then filters out WebApplicationExceptions:
@Provider
public class ExampleExceptionMapper implements ExceptionMapper<Throwable> {
private static final Logger log = ...;
public Response toResponse(Throwable t) {
if (t instanceof WebApplicationException) {
return ((WebApplicationException)t).getResponse();
} else {
log.error("Uncaught exception thrown by REST service", t);
return Response.status(Response.Status.INTERNAL_SERVER_ERROR)
// Add an entity, etc.
.build();
}
}
}
虽然这种方法可行，我觉得滥用ExceptionMappers应该用于什么，也就是说，将某些异常映射到某些响应。
While this approach may work, it feels to me like misuse of what ExceptionMappers are supposed to be used for, that is, mapping certain exceptions to certain responses.
大多数示例JAX-RS代码返回 响应 对象直接。按照这种方法，我可以将我的代码更改为：
Most sample JAX-RS code returns the Response object directly. Following this approach, I could change my code to something like:
public Response getUser(@PathParam("userId") Long userId) {
try {
User user;
user = loadUserByIdAndThrowApplicableWebApplicationExceptionIfNotFound(userId);
return Response.ok().entity(user).build();
} catch (Throwable t) {
return processException(t);
}
}
private Response processException(Throwable t) {
if (t instanceof WebApplicationException) {
return ((WebApplicationException)t).getResponse();
} else {
log.error("Uncaught exception thrown by REST service", t);
return Response.status(Response.Status.INTERNAL_SERVER_ERROR)
// Add an entity, etc.
.build();
}
}
但是，我对走这条路线很谨慎，因为我的实际项目不像这个例子那么简单，我必须一遍又一遍地实现这个相同的模式，更不用说必须手动建立响应。
However, I'm leery of going this route, as my actual project is not as simple as this example, and I would have to implement this same pattern over and over again, not to mention having to manually build up the Responses.
是否有更好的方法可以为未捕获的异常添加日志记录？
有没有正确的方式来实现这个？
Are there better methods for adding logging for uncaught exceptions? Is there a "right" way of implementing this?
推荐答案
由于缺乏更好的方法来实现日志记录未捕获的JAX-RS异常，使用全能 其他创意中的 ExceptionMapper ：＃1 似乎是添加此功能的最简洁，最简单的方法。
For lack of a better way to implement logging for uncaught JAX-RS exceptions, using a catch-all ExceptionMapper as in Other Ideas: #1 seems to be the cleanest, simplest way to add this functionality.
这是我的实现：
@Provider
public class ThrowableExceptionMapper implements ExceptionMapper<Throwable> {
private static final Logger log = Logger.getLogger(ThrowableExceptionMapper.class);
@Context
HttpServletRequest request;
@Override
public Response toResponse(Throwable t) {
if (t instanceof WebApplicationException) {
return ((WebApplicationException) t).getResponse();
} else {
String errorMessage = buildErrorMessage(request);
log.error(errorMessage, t);
return Response.serverError().entity("").build();
}
}
private String buildErrorMessage(HttpServletRequest req) {
StringBuilder message = new StringBuilder();
String entity = "(empty)";
try {
// How to cache getInputStream: http://stackoverflow.com/a/17129256/356408
InputStream is = req.getInputStream();
// Read an InputStream elegantly: http://stackoverflow.com/a/5445161/356408
Scanner s = new Scanner(is, "UTF-8").useDelimiter("\\A");
entity = s.hasNext() ? s.next() : entity;
} catch (Exception ex) {
// Ignore exceptions around getting the entity
}
message.append("Uncaught REST API exception:\n");
message.append("URL: ").append(getOriginalURL(req)).append("\n");
message.append("Method: ").append(req.getMethod()).append("\n");
message.append("Entity: ").append(entity).append("\n");
return message.toString();
}
private String getOriginalURL(HttpServletRequest req) {
// Rebuild the original request URL: http://stackoverflow.com/a/5212336/356408
String scheme = req.getScheme(); // http
String serverName = req.getServerName(); // hostname.com
int serverPort = req.getServerPort(); // 80
String contextPath = req.getContextPath(); // /mywebapp
String servletPath = req.getServletPath(); // /servlet/MyServlet
String pathInfo = req.getPathInfo(); // /a/b;c=123
String queryString = req.getQueryString(); // d=789
// Reconstruct original requesting URL
StringBuilder url = new StringBuilder();
url.append(scheme).append("://").append(serverName);
if (serverPort != 80 && serverPort != 443) {
url.append(":").append(serverPort);
}
url.append(contextPath).append(servletPath);
if (pathInfo != null) {
url.append(pathInfo);
}
if (queryString != null) {
url.append("?").append(queryString);
}
return url.toString();
}
}
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