Url-pattern matching rules for Servlets

About ContextPath:

Https://www.cnblogs.com/java-gwd/p/6495457.html

50,546,204 First you need to clarify a few confusing rules:

1. A matching rule in a servlet container is neither a simple wildcard nor a regular expression, but a specific rule. So don't use wildcard characters or regular expression matching rules to see the Url-pattern of Servlets.
2. Beginning with servlet 2.5, a servlet can use multiple Url-pattern rules,<servlet-mapping> tags to declare matching rules corresponding to the servlet, each <url-pattern> The label represents 1 matching rules;
3. When the servlet container receives a URL request initiated by the browser, the container subtracts the current app's context path with the URL, using the remaining string as the servlet map, if the URL is http://localhost:8080/appDemo/ Index.html, the application context is Appdemo, the container will http://localhost:8080/appDemo removed, with the rest of the/index.html part to do the servlet mapping match
4. Url-pattern mapping matching process is prioritized
5. And when a servlet match succeeds, it won't bother with the rest of the servlet.

One or four matching rules 1 Exact Match

　　The items configured in <url-pattern> must match exactly with the URL.

<Servlet-mapping><Servlet-name>myservlet</Servlet-name> <url-pattern< Span style= "COLOR: #0000ff" >>/user/users.html</ Url-pattern> < Url-pattern>/index.html</ url-pattern> << Span style= "COLOR: #800000" >url-pattern>/user/adduser.action </url-pattern>< Span style= "COLOR: #0000ff" ></servlet-mapping>  

When several URLs are entered in the browser, they are matched to the servlet
Http://localhost:8080/appDemo/user/users.html
Http://localhost:8080/appDemo/index.html
Http://localhost:8080/appDemo/user/addUser.action

　　

Attention:

http://localhost:8080/appDemo/user/addUser/is an illegal URL and will not be recognized as a http://localhost:8080/appDemo/user/addUser

In addition, the above URL can be followed by arbitrary query conditions, will be matched, such as

Http://localhost:8080/appDemo/user/addUser?username=Tom&age=23 will be matched to Myservlet.

2 Path Matching

　　A string that starts with a "/" character and ends with "/*" for path matching

　　

 <servlet-mapping > <servlet-name< Span style= "COLOR: #0000ff" >>myservlet</ Servlet-name> < Url-pattern>/user/*</ url-pattern></< Span style= "COLOR: #800000" >servlet-mapping>      

The path starts with/user/, and the following path can be arbitrary. For example, the following URLs will be matched.
Http://localhost:8080/appDemo/user/users.html
Http://localhost:8080/appDemo/user/addUser.action
Http://localhost:8080/appDemo/user/updateUser.actionl

3 extension matches

With "*." The string at the beginning is used for the extension match

<servlet-mapping>    <servlet-name>MyServlet</servlet-name>    <url-pattern>*.jsp </url-pattern>    <url-pattern>*.action</url-pattern></servlet-mapping>

Any URL requests that have an extension of JSP or action will match, such as the following URLs will be matched
http://localhost:8080/appDemo/user/users.jsp
Http://localhost:8080/appDemo/toHome.action

4 Default Match

　　

<servlet-mapping>    <servlet-name>myservlet</servlet-name< url-pattern>/</url-pattern></servlet-mapping> 

Second, the matching order

1. Exact Match, Servlet-mapping1:<url-pattern>/user/users.html</url-pattern>,servlet-mapping2:<url-pattern >/*</url-pattern>. When a request http://localhost:8080/appDemo/user/users.html comes, servlet-mapping1 matches, no longer matches with Servlet-mapping2
2. Path matching, first longest path match, and then shortest path match servlet-mapping1:<url-pattern>/user/*</url-pattern>,servlet-mapping2:< Url-pattern>/*</url-pattern>. When a request http://localhost:8080/appDemo/user/users.html comes, servlet-mapping1 matches, no longer matches with Servlet-mapping2
3. Extension matches, servlet-mapping1:<url-pattern>/user/*</url-pattern>,servlet-mapping2:<url-pattern>*. Action</url-pattern>. When a request http://localhost:8080/appDemo/user/addUser.action comes, servlet-mapping1 matches, no longer matches with Servlet-mapping2
4. Default match, no servlet found above, with default servlet, configured as <url-pattern>/</url-pattern>

Iii. issues needing attention 1 path matching and extension matching cannot be set at the same time

There are only three matching methods, either path matching ( beginning with the "/" character and ending with "/*" ) or extension matching ( "*."). Start ), either exact match, three matching methods cannot be combined, do not assume that wildcards or regular rules are used.

such as <url-pattern>/user/*.action</url-pattern> is illegal

Also note that:<url-pattern>/aa/*/bb</url-pattern> is precisely matched, legal, and here the * is not the meaning of the wildcard

2 "/*" and "/" do not have the same meaning

• "/*" is a path match and can match all request, because the path match priority is second only to the exact match, so "/*" overrides all extension matches, many 404 errors are caused, so this is a particularly bad match pattern, Generally only for filter url-pattern
• "/" is a special matching pattern in the servlet that has only one instance of the pattern, has the lowest priority, does not overwrite any other url-pattern, but replaces the built-in default servlet of the Servlet container, which also matches all request.
• After configuring "/", one possible phenomenon is that myservlet will intercept such as Http://localhost:8080/appDemo/user/addUser.action, http://localhost:8080/appDemo/ User/updateuser in the format of the request, but does not intercept http://localhost:8080/appDemo/user/users.jsp, http://localhost:8080/appDemo/ Index.jsp, this is because the servlet container should have a built-in "*.jsp" match, and the extension match has a higher precedence than the default match.

Tomcat configures the default servlet in the%catalina_home%\conf\web.xml file, with the following configuration code

　　

<Servlet><Servlet-name>default</Servlet-name><Servlet-class>org.apache.catalina.servlets.defaultservlet</Servlet-class><Init-param><Param-name>debug</Param-name><Param-value>0</Param-value></Init-param><Init-param><Param-name>listings</Param-name><Param-value>false</Param-value></Init-param><Load-on-startup>1</Load-on-startup></Servlet><Servlet><Servlet-name>jsp</Servlet-name><Servlet-class>org.apache.jasper.servlet.jspservlet</Servlet-class><Init-param><Param-name>fork</Param-name><Param-value>false</Param-value></Init-param><Init-param><Param-name>xpoweredby</Param-name><Param-value>false</Param-value></Init-param><Load-on-startup>3</Load-on-startup></Servlet><Servlet-mapping><Servlet-name>default</Servlet-name><Url-pattern>/</Url-pattern></Servlet-mapping><!--The mappings for the JSP servlet-<Servlet-mapping> <servlet-name< Span style= "COLOR: #0000ff" >>jsp</servlet-name< Span style= "COLOR: #0000ff" >> <url-pattern>*.jsp</url-pattern> <url-pattern>*.jspx</url-pattern></servlet-mapping>             

• Can read Http://stackoverflow.com/questions/4140448/difference-between-and-in-servlet-mapping-url-pattern
• "/*" and "/" will block the loading of static resources, requiring special attention

Iv. Examples of

The mapped URL	The corresponding servlet
/hello	Servlet1
/bbs/admin/*	Servlet2
/bbs/*	Servlet3
*.jsp	Servlet4
/	Servlet5

Results of Actual request mappings

Remove the remaining path of the context path	Servlet that handles the request
/hello	Servlet1
/bbs/admin/login	Servlet2
/bbs/admin/index.jsp	Servlet2
/bbs/display	Servlet3
/bbs/index.jsp	Servlet3
/bbs	Servlet3
/index.jsp	Servler4
/hello/index.jsp	Servlet4
/hello/index.html	Servlet5
/news	Servlet5

Url-pattern matching rules for Servlets