Filter執行順序

本文主要對 Filter 在前端提交後過濾器的順序進行測試

涉及的主要測試為 xml 配置測試及 註解 配置測試

註解 及 xml配置共存情況

• xml檔案配置

<filter>
    <filter-name>filter4</filter-name>
    <filter-class>filtertest.Demo4</filter-class>
</filter>
<filter-mapping>
    <filter-name>filter4</filter-name>
    <url-pattern>/servlet/*</url-pattern>
</filter-mapping>
<filter>
    <filter-name>filter3</filter-name>
    <filter-class>filtertest.Demo3</filter-class>
</filter>
<filter-mapping>
    <filter-name>filter3</filter-name>
    <url-pattern>/servlet/*</url-pattern>
</filter-mapping>
 

• 各個過濾器配置

@WebFilter("/servlet/*")
public class Demo1 implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("fliter1");
        chain.doFilter(request, response);
        System.out.println("fliter1back");
    }
}
 

@WebFilter("/servlet/*")
public class Demo2 implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("fliter2");
        chain.doFilter(request, response);
        System.out.println("fliter2back");
    }
}
 

public class Demo3 implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("fliter3");
        chain.doFilter(request, response);
    }
}

public class Demo4 implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("fliter4");
        chain.doFilter(request, response);
    }
}

• 測試結果穩定

  fliter4
  fliter3
  fliter1
  fliter2
  fliter2back
  fliter1back

• 猜測結論

  • xml一定優先註解

  • back方法執行順序和觸發順序正好相反

  • xml越上面配置越早觸發

  • 註解可能是因為名字字母的原因

    • 測試將 Demo2 類前面加一個 a 這樣就是 ADemo2

    • xml配置更換 Demo3 和 Demo4 的位置

      • 猜測結果

        fliter3
        fliter4
        fliter2
        fliter1
        fliter1back
        fliter2back

• 經測試結論正確

  • 結論
    • xml一定優先註解
    • back方法執行順序和觸發順序正好相反
    • xml越上面配置越早觸發
    • 註解根據字母順序觸發