title: 'Cannot subclass final class java.lang.String' when using Spring Boot 1.4 MockMVC controller method matching
body: <p>I have a MockMVC test and I'm trying to leverage the controller method matcher like so:</p>
  
  <pre><code>@Test
  public void environmentTopology() throws Exception {
      mockMvc.perform(get("/topology/{environmentId}", "envB"))
              .andExpect(handler().methodCall(on(ManagerController.class)
                   .environmentTopology("envB", true)));
  }
  </code></pre>
  
  <p>This should allow me to verify that the ManagerController's <code>environentTopology</code> method is called by the test. However instead I get the following exception:</p>
  
  <pre><code>java.lang.IllegalArgumentException: Cannot subclass final class java.lang.String
  
  at org.springframework.cglib.proxy.Enhancer.generateClass(Enhancer.java:565)
  at org.springframework.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25)
  at org.springframework.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:329)
  at org.springframework.cglib.proxy.Enhancer.generate(Enhancer.java:492)
  at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:93)
  at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:91)
  at org.springframework.cglib.core.internal.LoadingCache$2.call(LoadingCache.java:54)
  at java.util.concurrent.FutureTask.run(FutureTask.java:266)
  at org.springframework.cglib.core.internal.LoadingCache.createEntry(LoadingCache.java:61)
  at org.springframework.cglib.core.internal.LoadingCache.get(LoadingCache.java:34)
  at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData.get(AbstractClassGenerator.java:116)
  at org.springframework.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:291)
  at org.springframework.cglib.proxy.Enhancer.createHelper(Enhancer.java:480)
  at org.springframework.cglib.proxy.Enhancer.createClass(Enhancer.java:337)
  at org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilder.initProxy(MvcUriComponentsBuilder.java:611)
  at org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilder.access$000(MvcUriComponentsBuilder.java:89)
  at org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilder$ControllerMethodInvocationInterceptor.intercept(MvcUriComponentsBuilder.java:725)
  </code></pre>