update RequestParamParameterProcessor to support map param

[lowzj]

see issue #1097

[lowzj]

travis-ci build error, since travis-ci job #1353:

[ERROR] MavenReportException: Error while generating Javadoc: 
Exit code: 1 - /home/travis/.m2/repository/com/netflix/eureka/eureka-client/1.4.8/eureka-client-1.4.8.jar(com/netflix/discovery/DiscoveryClient.class): warning: Cannot find annotation method 'name()' in type 'Monitor': class file for com.netflix.servo.annotations.Monitor not found
...
[ERROR] Error fetching link: /home/travis/build/spring-cloud/spring-cloud-netflix/spring-cloud-netflix-eureka-client/target/apidocs/package-list. Ignored it.
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-source-plugin:3.0.0:jar (attach-sources) on project spring-cloud-netflix-eureka-server: Error creating source archive: Problem creating jar: Execution exception: Java heap space -> [Help 1]

[spencergibb]

yeah, we had to revert a fix for travis, don't worry about that.

[spencergibb]

@lowzj any chance you could add some tests?

[lowzj]

At first I run the test I wrote in this pr, it passed. Then I recompile the whole project, and test again, it failed. I create a new spring-boot project, include the spring-cloud-netflix-core dependency and run the same test again, it passed.

I debug the test and find the problem in my case, and I think probably there is something wrong in the method SpringMvcContract#synthesizeWithMethodParameterNameAsFallbackValue.

private Annotation synthesizeWithMethodParameterNameAsFallbackValue(
    Annotation parameterAnnotation, Method method, int parameterIndex) {
    ...
    String[] parameterNames = PARAMETER_NAME_DISCOVERER.getParameterNames(method);
    ...
}

The code above finally invokes the method java.lang.reflect.Executable#getParameters --> privateGetParameters --> getParameters0.
I'm not sure about the mechanism of java.lang.reflect.Executable#getParameters0, I find that it doesn't always return the expected result.

    public interface TestTemplate_MapParams {
        @RequestMapping(value = "/test", method = RequestMethod.GET)
        ResponseEntity<TestObject> getTest(@RequestParam Map<String, String> params);
    }

In this case , parameterNames expected result is ["params"].
In this project, getParameters0 return ["params"], and it's according to the class file. It's the expected result.
When I start a new project using the spring-cloud-netflix-core, getParameters0 return null then Executable synthesize all parameters' names('arg'+parameterIndex) and return ["arg0"]. arg0 is not according to the class file, so parameterNames would be null. So there is no fallback value for the annotation name/value attributes.

I haven't resolve this problem(may be not) now, but I think that only a simple property need a fallback value , such as String, Long, int... and so on.

[lowzj]

Finally, I find that java.lang.reflect.Executable#getParameters0 depends on compiler options

$ javac -help
...
-parameters                Generate metadata for reflection on method parameters
...

Then I add these code in my own project pom.xml

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <configuration>
                <compilerArgs>
                    <arg>-parameters</arg>
                </compilerArgs>
            </configuration>
        </plugin>
    </plugins>
</build>

the method java.lang.reflect.Executable#getParameters0 return the expected result.

[lowzj]

java documents explain my problem: Obtaining Names of Method Parameters

[spencergibb]

So -parameters is java 8 functionality and, except for a module or two, we are still baselined at java 7.

[lowzj]

thanks, I got it.

[lowzj]

@spencergibb Is there any suggestion about this pr?

[spencergibb]

@lowzj if this requires java 8 we won't be able to merge.

[lowzj]

@spencergibb it support java 7/8. I modify the SpringMvcContract#synthesizeWithMethodParameterNameAsFallbackValue to just affect simple properties.

[spencergibb]

Squashed and merged with a bit of polish via dc26b1e

[lynchlee]

👍