When we are doing Web applications, it is very common for errors to occur during request processing. Spring Boot provides a default mapping: When an exception is thrown in processing, it is /error forwarded to the request for processing, and the request has a global error page to display the exception content.
Choose a previously implemented web App (Chapter3-1-2) to start the app, access a nonexistent URL, or modify the processing to throw an exception directly, such as:
| 1234 | @RequestMapping ("/hello") Public String Hello() throws Exception {throw new Exception ("error occurred") ;} |
At this point, you can see an error page similar to the following, which is the default error mapping page provided by spring BOOT.
alt= default error page
Unified exception HandlingAlthough the default error mapping is implemented in Spring boot, in practice, your error page is not friendly to the user, and we usually need to implement our own exception hints.
Here we use the previous Web application example as the foundation (CHAPTER3-1-2), the transformation of unified exception processing.
@ControllerAdvice definition of a uniform exception-handling class, rather than being defined individually in each controller. To @ExceptionHandler define the type of exception the function is targeting, and finally map the exception object and the request URL to the error.html| 123456789101112131415 | @ControllerAdvice class Span class= "title" >globalexceptionhandler { public static final String default_error_view = "ERROR"; @ExceptionHandler (value = exception.class) public modelandview defaulterrorhandler (HttpServletRequest req, Exception e) throws Exception { Modelandview mav = new modelandview (); Mav.addobject ( "exception", e); Mav.addobject ( "url", Req.getrequesturl ()); Mav.setviewname (Default_error_view); return mav; } } |
error.html page display: Created in the templates directory error.html , the requested URL and the exception object's message output.| 123456789101112 | <! DOCTYPE html><html> <head lang="en" > <meta charset="UTF-8"/> <title> Unified exception Handling </title> </head> <body> <h1>error Handler</h1> <div th:text="${url}" ></div> <div th:text="${exception.message}" ></div> </body> </html> |
To launch the app, Access: http://localhost:8080/hello , you can see the following error prompt page.
alt= a custom error page
By implementing the above, we only need to Controller throw in the Exception , of course we may have a variety of different Exception . Then, in the @ControllerAdvice class, Exception match the @ExceptionHandler error mapping and processing according to the exception type that is configured in the specific type match that is thrown.
In the example above, @ControllerAdvice mapping to different error handling pages by unifying the different exception is defined. And when we want to implement the RESTful API, the error returned is JSON-formatted data, not HTML pages, which we can easily support.
Essentially, @ExceptionHandler @ResponseBody you can convert the contents of the return of the handler function into JSON format simply by adding it later.
The following is a concrete example to implement exception handling that returns JSON format.
| 12345678910111213 | public class errorinfo<t> { public static final Integer OK = 0 ; public static final Integer ERROR = + ; private Integer code; private String message; private String URL; private T data; //Omit getter and setter } |
| 1234567 | public class myexception extends Exception { public myexception (String message) { super (message);} } |
ControllerAdd JSON mappings, throw MyException exceptions| 123456789 | @Controller public class Hellocontroller { @RequestMapping ("/json")public String JSON() throws myexception {throw new MyException ("Error 2 occurred" );} } |
MyExceptioncreate a corresponding processing for an exception| 123456789101112131415 | @Controlle Radvice public class Globalexceptionhandler { @ExceptionHandler (value = Myexception.class) @ResponseBody Public errorinfo<string> jsonerrorhandlerthrows Exception { errorinfo<string> R = new errorinfo<> (); R.setmessage (E.getmessage ()); R.setcode (Errorinfo.error); R.setdata ( R.seturl (Req.getrequesturl (). toString ()); return r; } } |
| 123456 | {code: + ,data: " Some data",message: "Error 2 occurred",URL: "http://localhost:8080/ JSON "} |
Now that you have finished creating uniform exception handling in spring boot, the actual implementation is still dependent on spring MVC annotations, and more in-depth use can refer to the documentation for spring MVC.
Complete example of this article: chapter3-1-6
Spring-boot Combat "07" "Turn": Unified exception handling for Web applications in Spring boot
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