HTTP Status 404 (The requested resource is not available)": The exception is mainly caused by ① path error ② spelling error
The workaround is as follows:
1. Web application is not deployed;
2. URL is entered incorrectly;
a. Check whether the IP address and port number of the URL are written correctly;
b. Check whether the context path is correct Project-------Properties------MyElipse-----Web----- Web Context-root Check whether the path name is written correctly;
c. Check whether the file name is written correctly;
3. Directory cannot be referenced
Check where the files are stored in Eclipse's "Package Explorer". Since the content in the META-INF WEB-INF folder cannot be published externally, if you reference files with these two directories, it is definitely not allowed
eg: http://localhost:8080/guestbook/WEB-INF/index.html is wrong, the file location is wrong
4. Problem in web.xml in Tomcat server
If your web application has multiple jsp pages, you may get a 404 error when you click on the virtual root directory of your web application, but you only need to modify the web.xml in the Tomcat server
<init-param>
<param-name>listing</param-name>
<param-value>false (change it to true)</param-value>
</init-param>
5. There must be several fixed folders and files under WEB-INF
web.xml configuration file for the web app;
lib The library file used by the web app;
classes store the compiled servlet;
<servlet>
<servlet-name>HelloWorldServletservlet-name
<servlet-class>HelloWorldServlet</servlet-class>
</servlet>
Please pay attention to their names, so as not to misspelled wasted effort to find errors.
6. If you want to run a servlet (.class) file instead of a .jsp file, configure web.xml (under WEB-INF, of course), and add the following fields:
<servlet>
<servlet-name>HelloWorldServlet<servlet-name>
<servlet-class>HelloWorldServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloWorldServlet</servlet-name>
<url-pattern>/HelloWorldServlet</url-pattern>
</servlet-mapping>
Where "HelloWorldServlet" is changed to the file name you want to run .