The principle analysis of filter to solve the request parameter garbled code

This article is about SpringMVC appear request Solution to the problem of request parameter garbled Blog “ Solutions 1” Principle analysis of , Personally, I think it is very helpful to understand the principles behind some simple technologies for personal programming .
If there is request Friends who ask for parameter garbled problems can check the blog I mentioned above , I hope that's helpful ！

1、 Get into CharacterEncodingFilter.class

2、CharacterEncodingFilter Inherited structure diagram

​ It can be seen that CharacterEncodingFilter My great grandfather was Filter

3、doFilter( ) Method

​ Let's focus on Filter Interface doFilter( ) Implementation of method ：

​ doFilter( ) Method in OncePerRequestFilter To realize ：

​ The key ：doFilter( ) The method is implemented doFilterInternal( ), and doFilterInternal( ) The implementation of the method is OncePerRequestFilter Subclasses of CharacterEncodingFilter To realize .

​ I went around and back to CharacterEncodingFilter The class , Look at the key code ：

4、 In retrospect web.xml Configuration information in

5、CharacterEncodingFilter Properties in a class

​ View the source code ,CharacterEncodingFilter Class has three properties , And found that whether there is a parameter or no parameter construction method forceRequestEncoding、

forceResponseEncoding The initial values of these two attributes are false. The main purpose of the following is to explain why it should be changed to ture？

6、 Key code

​ 1、 We are web.xml Set up inside. encoding by UTF-8, So the value is not empty .

​ 2、 We are web.xml Set up inside. forceRequestEncoding、forceResponseEncoding Two Boolean The value is true, therefore if Statement can be executed

That's ok .

​ 3、 Separately request、response The encoding of is set to encoding, That is to say UTF-8.

Here we are , End of analysis ！