MatrixVariable position with Tomcat and Undertow

[sydneyhenrard]

I defined a REST endpoint that accepts a MatrixVariable. I did some testing, and concluded that the MatrixVariable is not processed the same way depending on the container. The v1 endpoint ends with a "static" path, whereas the v2 endpoint ends with a PathVariable.

@RestController
public class BugResource {
    @GetMapping(value = "/v1/{a}/plus/{b}/equal", produces = MediaType.APPLICATION_JSON_VALUE)
    public ResponseEntity<String> bug(
            @PathVariable String a,
            @PathVariable String b,
            @MatrixVariable(required = false) String matrix
    ) {
        return ResponseEntity.ok(a + " " + b + " " + matrix);
    }

    @GetMapping(value = "/v2/{a}/plus/{b}", produces = MediaType.APPLICATION_JSON_VALUE)
    public ResponseEntity<String> bug2(
            @PathVariable String a,
            @PathVariable String b,
            @MatrixVariable(required = false) String matrix
    ) {
        return ResponseEntity.ok(a + " " + b + " " + matrix);
    }
}

Then I tried to call the REST endpoint:

with Tomcat
http://localhost:8080/v1/a;matrix=matrix/plus/b/equal => 200
http://localhost:8080/v1/a/plus/b;matrix=matrix/equal => 200
http://localhost:8080/v2/a/plus/b;matrix=matrix => 200
http://localhost:8080/v2/a;matrix=matrix/plus/b => 200

with Undertow
http://localhost:8080/v1/a;matrix=matrix/plus/b/equal => 404
http://localhost:8080/v1/a/plus/b;matrix=matrix/equal => 404
http://localhost:8080/v2/a/plus/b;matrix=matrix => 200
http://localhost:8080/v2/a;matrix=matrix/plus/b => 404

So it seems that Undertow only deals with MatrixVariable when the endpoint ends with a PathVariable, and the MatrixVariable is placed at the end of the endpoint

To reproduce, I just created a Spring Initializr maven project:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>matrixparam</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>matrixparam</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-tomcat</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-undertow</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

The configuration to enable MatrixVariable:

@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void configurePathMatch(PathMatchConfigurer configurer) {
        UrlPathHelper urlPathHelper = new UrlPathHelper();
        urlPathHelper.setRemoveSemicolonContent(false);
        configurer.setUrlPathHelper(urlPathHelper);
    }
}

[bclozel]

Hi @sydneyhenrard

I managed to reproduce this behavior with standalone Undertow, no Spring involved. See the following code snippet:

import io.undertow.Undertow;
import io.undertow.server.HttpHandler;
import io.undertow.server.HttpServerExchange;
import io.undertow.util.Headers;

class Scratch {
  public static void main(String[] args) {
    Undertow server = Undertow.builder()
        .addHttpListener(8080, "localhost")
        .setHandler(new HttpHandler() {
          @Override
          public void handleRequest(final HttpServerExchange exchange) throws Exception {
            exchange.getResponseHeaders().put(Headers.CONTENT_TYPE, "text/plain");
            exchange.getResponseSender().send(exchange.getRequestPath());
          }
        }).build();
    server.start();
  }
}

$ curl -v http://localhost:8080/v2/a\;matrix\=matrix/plus/b
HTTP/1.1 200 OK
Connection: keep-alive
Content-Length: 5
Content-Type: text/plain
Date: Tue, 18 Dec 2018 22:53:08 GMT

/v2/a

The path information seems to be incorrect, and Spring Framework after that calls request.getServletContext() which returns "/v2/a". From that point, the request information is wrong and there's no way to correctly map the request to the controller. Tomcat in this case returns "" as the context path, as expected.

Looking at io.undertow.server.protocol.http.HttpRequestParser, it seems the parsing of the HTTP request path stops at the first encounter of a matrix variable on a path segment.

I might have missed something here - maybe I misunderstand the way undertow behaves, or I missed a specific configuration property. But could you raise an issue against the Undertow project and report back here?

Thanks for your report!

[chrsoo]

The issue is managed in UNDERTOW-1464.

[chrsoo]

@bclozel it seems to be possible to implement a custom URL parser by setting the UndertowOptions.DECODE_URL to false and implementing an URLDecodingHandler, cf Carter Kozak's comment on UNDERTOW-1464

Although the ideal solution of course would be to fix the underlying Undertow issue would you consider this workaround in the Spring code for Undertow?

I have not yet looked into how feasible this would be but I am willing to invest some time if you think it a viable alternative.

[philwebb]

@chrsoo It feels like that workaround might cause issues elsewhere and is a bit risky for us apply by default. I think we should wait to see how UNDERTOW-1464 plays out.

[chrsoo]

@philwebb, @bclozel I have opened PR 832 for UNDERTOW-1464 - would love your feedback on how it would affect the downstream Spring Boot project - any suggestions are welcome!

In particular it would be good to know whether the getRequestPath() method should return the path including or excluding matrix parameters...