What are meta-inf and WEB-INF respectively?

1. summary
I'm learning spring.factories When I found myself for META-INF and WEB-INF The role of , So here is a supplement .

META-INF The main function of is to Jar A description of the package . Its meaning is （meta information） Signature folder . Packing jar It will be generated automatically , Of course, you can also modify the configuration manually .

WEB-INF yes Java Of WEB Security directory of application . The so-called security is that the client cannot access , Only the server can access the directory .

2. detailed
2.1 Explanation on Baidu
META-INF It's like a packet , The files and directories in the directory get Java 2 Recognition and interpretation of the platform , Used to configure applications 、 add-in 、 Class loaders and services manifest.mf file , In use jar Automatically generated when packaging .

WEB-INF yes Java Of WEB Security directory of application . The so-called security is that the client cannot access , Only the server can access the directory . If you want to access the files directly in the page , Must pass web.xml The file can only be accessed by mapping the file to be accessed .

2.2 mainfest.mf file
Means manifest file ,manifest Every line in the file is key－value Corresponding : Property name starts with , Next is “:” , Then there is the attribute value , The most in each line 72 Characters , Add if necessary , You can continue on the next line , The continuation line begins with a space , A line that begins with a space is considered a continuation of the previous line . There are usually these fields ：
 

Manifest-Version: 1.0
Built-By: Dxy
Created-By: IntelliJ IDEA
Build-Jdk: 1.8.0_144

The message is jar Description of the document ：

Manifest-Version： Generated  manifest.mf  Version of a file 
Built-By： The creation of the file is named by the user , stay  IDEA  Can be set in the configuration file 
Created-By： The generator of the file , Generally by jar Command line tool generation , When shown here  idea
Bulid-Jdk： What is used  JDK  Environmental Science 

And these properties ：

 One 、 General properties 
 
1：Signature-Vresion： Definition  jar  Signed version of the document 
 
2：Class-Path： Internal class search path , Provided to the application or class loader 
 
 Two 、 Application related properties 
 
1、Main-Class： Definition  jar  File entry class , This class must be executable ！ Once this attribute is defined, you can use 
 
java -jar  The program name .jar  To run the  jar  file 

2.3  and WEB-INF The difference between

META-INF Deposit is jar Package label information ,jar There will be this folder ,war There will be .

and WEB-INF yes java web A folder unique to the application , Belong to web Security directory of application , The directory client cannot access , Only the server can access . If you want to access the files directly in the page , Must pass web.xml The file can only be accessed by mapping the file to be accessed . So if there are hyperlinks in our pages <a> Labels or <script></script> Under the script location.href Go straight to WEB-INF Next one jsp perhaps html page , Then you can't quote , Because such a request mode is the request of the client .css/js/html There is no need to put it in WEB-INF Next . Finally, these will be displayed intact on the client , So access security won't be a problem at all .

jsp Put it in web-inf Next , There are two main reasons

The patterns of ancient times will put the business logic , Database connection and other sensitive information are written in jsp Inside , Being directly accessed by users will have security problems .
This is no longer a problem in the modern model , Should not be a problem .

jsp It runs on the server side , And it usually needs other programs to support —— For example, the data can be processed in the background jsp Apply colours to a drawing etc. , It doesn't make sense for users to directly access one , Second, the exception will be thrown , All this wastes server resources .

For systems with strict safety requirements , You are not allowed to visit your jsp file , You can put it in web-inf below , For systems with less stringent security requirements , You can put it directly in webroot below .

3. summary
META-INF comparison WEB-INF It is usually used less in daily development , Generally, the fields are construction tools or IDE Automatically generated .

4.META-INF What is it for

Web Project WEB-INF Instructions for using the catalog