对Filter执行顺序的测试

Filter执行顺序

本文主要对 Filter 在前端提交后过滤器的顺序进行测试

涉及的主要测试为 xml 配置测试及 注解 配置测试

注解 及 xml配置共存情况

• xml文件配置

<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>

• 各个过滤器配置

@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);
    }
}

• 测试结果稳定

  fliter4
  fliter3
  fliter1
  fliter2
  fliter2back
  fliter1back

• 猜测结论

  • xml一定优先注解

  • back方法执行顺序和触发顺序正好相反

  • xml越上面配置越早触发

  • 注解可能是因为名字字母的原因

    • 测试将 Demo2 类前面加一个 a 这样就是 ADemo2

    • xml配置更换 Demo3 和 Demo4 的位置

      • 猜测结果

        fliter3
        fliter4
        fliter2
        fliter1
        fliter1back
        fliter2back

• 经测试结论正确

  • 结论
    • xml一定优先注解
    • back方法执行顺序和触发顺序正好相反
    • xml越上面配置越早触发
    • 注解根据字母顺序触发