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How to get form parameters in request filter

由 匆匆过客 提交于 2019-12-03 12:37:44

This was a tricky one. I'd removed other Jersey filters to eliminate them from the problem, but missed a plain servlet filter hiding at the bottom of web.xml:

<filter>
    <filter-name>myFilter</filter-name>
    <filter-class>com.application.my.MyFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>myFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

Removing this filter fixed the issue - form params showed up in the Jersey filter. But why? I dug deeper, narrowing down the problem to a single statement in MyFilter:

request.getParameter("some_param")

I tried to simplify the problem even more by removing MyFilter and making the same call in the Jersey filter (by injecting HttpServletRequest) - but the form parameters still showed up. The issue appears to happen specifically when calling getParameter on the org.apache.catalina.connector.RequestFacade instance that gets passed into javax.servlet.Filter.doFilter. So is this in fact a Tomcat bug?

The documentation of ServletRequest.getParameter says:

If the parameter data was sent in the request body, such as occurs with an HTTP POST request, then reading the body directly via getInputStream() or getReader() can interfere with the execution of this method.

So maybe the reverse is true too - that calling getParameter might be allowed to interfere with the entity input stream? It's unclear to me whether the method's contract allows for this behavior, and whether it indicates a bug in Tomcat, Jersey, or neither.

Anyway, that old filter wasn't actually needed so my issue is solved but just removing it.

Here's a full reproduction of the problem (Tomcat 7.0):

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
    <display-name>test</display-name>
    <servlet>
        <servlet-name>jersey</servlet-name>
        <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>com.sun.jersey.config.property.packages</param-name>
            <param-value>com.application.my</param-value>
        </init-param>
        <init-param>
            <param-name>com.sun.jersey.spi.container.ResourceFilters</param-name>
            <param-value>com.application.my.TestFilterFactory</param-value>
        </init-param>
        <init-param>
            <param-name>com.sun.jersey.config.feature.Trace</param-name>
            <param-value>false</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>jersey</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
    <filter>
        <filter-name>servletFilter</filter-name>
        <filter-class>com.application.my.TestServletFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>servletFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

TestServletFilter.java:

package com.application.my;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public final class TestServletFilter implements Filter {

    @Override
    public void init(FilterConfig config) { }

    @Override
    public void doFilter(
            final ServletRequest request,
            final ServletResponse response,
            final FilterChain chain
    ) throws IOException, ServletException {
        System.out.println("calling getParameter on " + request.getClass().getName());
        request.getParameter("blah");
        chain.doFilter(request, response);
    }

    @Override
    public void destroy() { }
}

TestFilterFactory.java:

package com.application.my;

import java.util.Collections;
import java.util.List;

import com.sun.jersey.api.model.AbstractMethod;
import com.sun.jersey.spi.container.ContainerRequest;
import com.sun.jersey.spi.container.ContainerRequestFilter;
import com.sun.jersey.spi.container.ContainerResponseFilter;
import com.sun.jersey.spi.container.ResourceFilter;
import com.sun.jersey.spi.container.ResourceFilterFactory;

public final class TestFilterFactory implements ResourceFilterFactory {

    @Override
    public List<ResourceFilter> create(final AbstractMethod method) {
        return Collections.<ResourceFilter>singletonList(new ResourceFilter() {
            @Override
            public ContainerRequestFilter getRequestFilter() {
                return new ContainerRequestFilter() {
                    @Override
                    public ContainerRequest filter(final ContainerRequest request) {

                        System.out.println("form: " + request.getFormParameters());

                        return request;
                    }
                };
            }
            @Override
            public ContainerResponseFilter getResponseFilter() {
                return null;
            }
        });
    }
}

TestResource.java:

package com.application.my;

import java.net.URI;

import javax.ws.rs.Consumes;
import javax.ws.rs.FormParam;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;


@Path("/post-stuff")
@Produces(MediaType.APPLICATION_JSON)
public final class TestResource {

    @POST
    @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
    public Response execute(
            @FormParam("form_param_1") final String formParam1,
            @FormParam("form_param_2") final String formParam2
    ) {
        System.out.println("form param_1: " + formParam1);
        System.out.println("form param_2: " + formParam2);

        return Response.created(URI.create("/")).entity("{}").build();
    }
}

Make sure your ResourceFilterFactory creates an instance of ResourceFilter for the TestResource#execute method, which then creates a ContainerRequestFilter instance:

public class MyFilterFactory implements ResourceFilterFactory {

    @Override
    public List<ResourceFilter> create(final AbstractMethod am) {
        return new ArrayList<ResourceFilter>() {{

            add(new ResourceFilter() {
                @Override
                public ContainerRequestFilter getRequestFilter() {
                    return new ContainerRequestFilter() {
                        @Override
                        public ContainerRequest filter(final ContainerRequest request) {
                            System.out.println(request.getFormParameters());
                            return request;
                        }
                    };
                }

                @Override
                public ContainerResponseFilter getResponseFilter() {
                    return null;
                }
            });
        }};
    }
}

From the trace you have provided I am not sure whether your ContainerRequestFilter is called. There should be one more trace header containing something like this:

→matched message body reader: class com.sun.jersey.api.representation.Form, "application/x-www-form-urlencoded" -> com.sun.jersey.core.impl.provider.entity.FormProvider@b98df1f

The whole trace from my test:

HTTP/1.1 201 Created
Location: http://localhost:8080/helloworld-webapp/helloworld/
Content-Type: text/plain
X-Jersey-Trace-000: accept root resource classes: "/helloworld"
X-Jersey-Trace-001: match path "/helloworld" -> "/application\.wadl(/.*)?", "/helloworld(/.*)?"
X-Jersey-Trace-002: accept right hand path java.util.regex.Matcher[pattern=/helloworld(/.*)? region=0,11 lastmatch=/helloworld]: "/helloworld" -> "/helloworld" : ""
X-Jersey-Trace-003: accept resource: "helloworld" -> @Path("/helloworld") com.sun.jersey.samples.helloworld.resources.HelloWorldResource@7449df0f
X-Jersey-Trace-004: match path "" -> ""
X-Jersey-Trace-005: accept resource methods: "helloworld", POST -> com.sun.jersey.samples.helloworld.resources.HelloWorldResource@7449df0f
X-Jersey-Trace-006: matched resource method: public javax.ws.rs.core.Response com.sun.jersey.samples.helloworld.resources.HelloWorldResource.execute(java.lang.String,java.lang.String)
X-Jersey-Trace-007: matched message body reader: class com.sun.jersey.api.representation.Form, "application/x-www-form-urlencoded" -> com.sun.jersey.core.impl.provider.entity.FormProvider@6bc1b916
X-Jersey-Trace-008: matched message body reader: class com.sun.jersey.api.representation.Form, "application/x-www-form-urlencoded" -> com.sun.jersey.core.impl.provider.entity.FormProvider@6bc1b916
X-Jersey-Trace-009: matched message body writer: java.lang.String@f62, "text/plain" -> com.sun.jersey.core.impl.provider.entity.StringProvider@4aae6c4e
Transfer-Encoding: chunked
Server: Jetty(6.1.24)

EDIT 1:

Enable request LoggingFilter:

<init-param>
    <param-name>com.sun.jersey.spi.container.ContainerRequestFilters</param-name>
    <param-value>com.sun.jersey.api.container.filter.LoggingFilter</param-value>
</init-param>

EDIT 2:

Also make sure no other Servlet or Jersey filter has read the InputStream before. In such a case the entity input stream may no longer be available (but you can still inject @FormParam into your resource method - as in this case).

标签
java
jersey
http-post
http-request
jersey-1.0
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