Shulou(Shulou.com)06/03 Report--

This article mainly introduces "the use scene of SpringMVC@ControllerAdvice". In the daily operation, I believe that many people have doubts about the use of SpringMVC@ControllerAdvice. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubts about "the use scene of SpringMVC@ControllerAdvice"! Next, please follow the editor to study!

@ ControllerAdvice, many beginners may not have heard of this annotation, in fact, this is a very useful annotation, as the name implies, this is an enhanced Controller. With this Controller, you can achieve three functions:

Global exception handling global data binding global data preprocessing

Flexible use of these three functions can help us simplify a lot of work. It is important to note that this is a function provided by SpringMVC and can be used directly in Spring Boot, as shown below.

Global exception handling

To implement global exception handling using @ ControllerAdvice, you only need to define a class, which can be defined as follows:

@ ControllerAdvicepublic class MyGlobalExceptionHandler {@ ExceptionHandler (Exception.class) public ModelAndView customException (Exception e) {ModelAndView mv = new ModelAndView (); mv.addObject ("message", e.getMessage ()); mv.setViewName ("myerror"); return mv;}}

In this class, multiple methods can be defined, and different methods handle different exceptions, such as methods that specifically deal with null pointers, methods that specifically deal with array out of bounds. You can also handle all exception information in one method, just like the code above

The @ ExceptionHandler annotation is used to indicate the handling type of the exception, that is, if NullpointerException is specified here, the array out-of-bounds exception will not come into this method.

Global data binding

The global data binding feature can be used to do some initialized data operations, and we can define some common data in the classes annotated with @ ControllerAdvice, so that the resulting data can be accessed in every Controller interface.

To use the steps, first define the global data, as follows:

@ ControllerAdvicepublic class MyGlobalExceptionHandler {@ ModelAttribute (name = "md") public Map mydata () {HashMap map = new HashMap (); map.put ("age", 99); map.put ("gender", "male"); return map;}}

Use the @ ModelAttribute annotation to mark that the returned data of this method is a global data. By default, the key of this global data is the returned variable name, and value is the returned value of the method. Of course, developers can reassign the key through the name attribute of the @ ModelAttribute annotation.

After the definition is completed, the data defined here can be obtained in any of the Controller APIs:

@ RestControllerpublic class HelloController {@ GetMapping ("/ hello") public String hello (Model model) {Map map = model.asMap (); System.out.println (map); int I = 1 / 0; return "hello controller advice";}}

Global data preprocessing

Consider that I have two entity classes, Book and Author, defined as follows:

Public class Book {private String name; private Long price; / / getter/setter} public class Author {private String name; private Integer age; / / getter/setter}

At this point, if I define a data add interface, as follows:

@ PostMapping ("/ book") public void addBook (Book book, Author author) {System.out.println (book); System.out.println (author);}

At this point, the add operation is problematic because both entity classes have a name attribute that cannot be distinguished when passed from the front end. At this point, the global data preprocessing of @ ControllerAdvice can solve this problem.

The resolution steps are as follows:

1. Alias the variable in the interface

@ PostMapping ("/ book") public void addBook (@ ModelAttribute ("b") Book book, @ ModelAttribute ("a") Author author) {System.out.println (book); System.out.println (author);}

two。 Preprocess the request data

Add the following code to the class of the @ ControllerAdvice tag:

InitBinder ("b") public void b (WebDataBinder binder) {binder.setFieldDefaultPrefix ("b.");} @ InitBinder ("a") public void a (WebDataBinder binder) {binder.setFieldDefaultPrefix ("a.");}

The @ InitBinder ("b") annotation indicates that the method is used to handle Book and related parameters. In the method, add a b prefix to the parameter, that is, the request parameter should have a b prefix.

3. Send a request

When the request is sent, the parameters can be distinguished by adding different prefixes to the parameters of different objects.

At this point, the study on the "usage scenario of SpringMVC@ControllerAdvice" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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