Code generation: create interface for class

Question

I'm writing a util to generate interface for class using Apache Velocity. Currently it uses the following dtos:

public class ClassDescriptor {
  private String name;
  private List<MethodDescriptor> methods;
  // getters/setters
}

public class MethodDescriptor {
  private String name;
  private String returnType;
  private List<ParamDescriptor> parameters;
  // getters/setters
}

public class ParamDescriptor {
  public String name;
  public String type;
  public List<String> generics;
  // getters/setters
}

Here is the code used at the moment:

final Class<?> clazz;
final ClassDescriptor classDescriptor = new ClassDescriptor();
final List<MethodDescriptor> methodDescriptors = new ArrayList<MethodDescriptor>();
for (Method method : clazz.getDeclaredMethods()) {
  final MethodDescriptor methodDescriptor = new MethodDescriptor();
  final Paranamer paranamer = new AdaptiveParanamer();
  final String[] parameterNames = paranamer.lookupParameterNames(method, false);
  final List<ParamDescriptor> paramDescriptors = new ArrayList<ParamDescriptor>();

  for (int i = 0; i < method.getParameterTypes().length; i++) {
    final ParamDescriptor paramDescriptor = new ParamDescriptor();
    paramDescriptor.setName(parameterNames[i]);
    paramDescriptors.add(paramDescriptor);
    paramDescriptor.setType(method.getGenericParameterTypes()[i].toString().replace("class ", ""));
  }
  methodDescriptor.setParameters(paramDescriptors);
  methodDescriptor.setName(method.getName());

  methodDescriptor.setReturnType(method.getGenericReturnType().toString());
  methodDescriptors.add(methodDescriptor);
}
classDescriptor.setMethods(methodDescriptors);
classDescriptor.setName(simpleName);

The ????? should contain code to get a list of generics for the parameter and that is the problem, I still can't find a way to do that. I'm using the following test class:

public class TestDto {
  public void test(Map<Double, Integer> test) {
  }
}

How can I get this information? I've already tried ParameterizedType with no luck.

Update: the code above is now working.

Joop Eggen · Accepted Answer · 2013-08-16 14:23:27Z

1

    Class<TestDto> klazz = TestDto.class;
    try {
        Method method = klazz.getDeclaredMethod("test", Map.class);
        Type type = method.getGenericParameterTypes()[0];
        System.out.println("Type: " + type);
    } catch (NoSuchMethodException ex) {
        Logger.getLogger(App.class.getName()).log(Level.SEVERE, null, ex);
    } catch (SecurityException ex) {
        Logger.getLogger(App.class.getName()).log(Level.SEVERE, null, ex);
    }

    Type: java.util.Map<java.lang.Double, java.lang.Integer>

Because of type erasure, this still is generous information. Not heared from any push towards runtime generic type usage.

answered Aug 16, 2013 at 14:23

Joop Eggen

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1 Comment

Yurii Shylov Over a year ago

Very good! The main problem for me was to get the generic classes to add them to import list. I've forgot that we can just use the full path like java.util.blablabla. Also there is a small problem with simple classes cause it returns "class java.util.String". Currently I'm using paramDescriptor.setType(method.getGenericParameterTypes()[i].toString().replace("class ", "")). Not very ellegant but works. I have to check if this is suitable for return types, after that I'll aprove the answer.

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