jsp - 如何制作 URL 过滤器以使用 Servlet 路由操作？

Question

我目前正在开发一个 Java EE 网络框架，我想知道如何路由我的 URL...我想要支持 HMVC 功能! URL 将遵循此规则:

/module_name/controller_name/action_name，其中:

模块名称:由斜杠分隔的路径...例如:模块“X”的子模块“Y”:/X/Ycontroller_name:没有特殊字符的 Controller 名称action_name: 没有特殊字符的 Action 名称

我想将/module_name/controller_name/映射到特定的 servlet Controller ! Action 部分是该类的公共(public)方法! :)

我怎么能做到这一点？使用过滤器？如果可能的话，我想要一个例子!

Answer 1

我看到 3 种方法:过滤器、基本 servlet(所有请求都通过主 servlet)或“servlet-mapping”

过滤器

本例重写url

http://example.org/<int value>

to

http://example.org/user?id=<int value>

i.e

http://example.org/1234 -> http://example.org/user?id=1234

1. determinate filter in web.xml

<filter>
    <filter-name>Router</filter-name>
    <filter-class>org.example.Router</filter-class>
    <init-param>
        <param-name>param1</param-name>
        <param-value>valueOfparam1</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>Router</filter-name>
    <url-pattern>/*</url-pattern> 
</filter-mapping>

in init-param section you can specify route rules

1. filter class

   public class Router implements javax.servlet.Filter {
   
   private static final Pattern REWRITE_PATTERN = Pattern.compile("(^[1-9]\\d*)$");
   
   @Override
   public void destroy() {
   }
   
   @Override
   public void doFilter(ServletRequest req, ServletResponse res, FilterChain fc) throws IOException, ServletException {
   //this method calling before controller(servlet), every request
   
       HttpServletRequest request = (HttpServletRequest) req;
       String url = request.getRequestURL().toString();
       String number = url.substring(url.lastIndexOf("/")).replace("/", "");
   
       Matcher m = REWRITE_PATTERN.matcher(number);
       if(m.find()) {
           RequestDispatcher dispatcher = request.getRequestDispatcher("user?id=" + m.group(1));
           dispatcher.forward(req, res);
       } else {
           fc.doFilter(req, res);
       }
   }
   
   @Override
   public void init(FilterConfig fc) throws ServletException {
       //here you may read params from web.xml
   }}
   

基本 sevlet

public class BasicServlet extends HttpServlet {
   //route rules here, and rewrite
}

servlet 映射

<servlet-mapping>
    <servlet-name>UserServlet</servlet-name>
    <uri-mapping>/user/*</uri-mapping>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>PostServlet</servlet-name>
    <uri-mapping>/post/*</uri-mapping>
</servlet-mapping>

• 过滤器 - 更灵活，不需要认真修改工作代码
• 基本 servlet - 灵活，需要更改代码
• servlet 映射 - 简单，不灵活(针对特定路由规则)