使Servlet 2.5代码与Servlet 3.0兼容，反之亦然

Question

I have a class that implements javax.servlet.Filter and inside that filter, I'm instantiating an instance of InterceptHttpRequestFilter and InterceptHttpResponseFilter (which are used to modify the incoming and outgoing request and response)

Example:

public class InterceptHttpRequestFilter implements HttpServletRequest {

    private HttpServletRequest httpReq;
    final StringBuffer sb = new StringBuffer();

    public InterceptHttpRequestFilter(ServletRequest request) {
        this.httpReq = (HttpServletRequest) request;
        try {
            StringWriter sw = new StringWriter();
            IOUtils.copy(request.getInputStream(), sw);
            sb.append(sw.getBuffer().toString());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    ....

When deploying this project on Tomcat6 using Servlet 2.5, everything works as it should. Deploy it on Tomcat 7 and I get an AbstractMethodError:

SEVERE: Servlet.service() for servlet [_______] in context with path [/__________-1.0.0] threw exception [Filter execution threw an exception] with root cause
java.lang.AbstractMethodError
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:225)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at com.mycee.project.filter.MyFilter.doFilter(MyFilter.java:182)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
        at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:315)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:744)

The obvious solution is to implement all the missing methods required by Servlet Version 3's HttpRequest / Response interfaces.

The maven dependency on mvnrepository is still in alpha:

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>servlet-api</artifactId>
    <version>3.0-alpha-1</version>
</dependency>

So my question is, does middle ground exist that will allow me to run this project on both Tomcat6 (Servlet 2.5) and Tomcat7 (Servlet 3.0) without having to tinker with my InterceptHttpRequestFilter and InterceptHttpResponseFilter ?

Answer 1

That's why it's recommended to extend HttpServletRequestWrapper instead of implementing HttpServletRequest directly.

HttpServletRequestWrapper has implementations of all required methods, therefore it should solve the problem.