如何获取对象构造函数的参数名称（反射）？ [复制]

假设我以某种方式从其他类获得了对象引用：

Object myObj = anObject;

现在我可以获得这个对象的类：

Class objClass = myObj.getClass();

现在，我可以获得该类的所有构造函数：

Constructor[] constructors = objClass.getConstructors();

现在，我可以循环每个构造函数：

if (constructors.length > 0)
{
    for (int i = 0; i < constructors.length; i++)
    {
        System.out.println(constructors[i]);
    }
}

这已经给了我一个关于构造函数的很好的总结，例如构造函数 public Test(String paramName) 显示为 public Test(java.lang.String)

然而，我不想给我类类型，而是想获取参数的名称..在本例中为“paramName”。我该怎么做呢？我尝试了以下操作但没有成功：

if (constructors.length > 0)
    {
        for (int iCon = 0; iCon < constructors.length; iCon++)
        {
            Class[] params = constructors[iCon].getParameterTypes();
            if (params.length > 0)
            {
                for (int iPar = 0; iPar < params.length; iPar++)
                {
                    Field fields[] = params[iPar].getDeclaredFields();
                    for (int iFields = 0; iFields < fields.length; iFields++)
                    {
                        String fieldName = fields[i].getName();
                        System.out.println(fieldName);
                    }                                       
                }
            }
        }
    }

不幸的是，这并没有给我预期的结果。谁能告诉我我应该怎么做或者我做错了什么？谢谢！

正如评论中提到的罗曼的回答 https://stackoverflow.com/questions/2729580/how-to-get-the-parameter-names-of-an-objects-constructors-reflection/2729595#2729595, 参数名称can如果编译器包含调试符号，则可以检索，但不是通过标准 Java Reflection API。下面的示例说明了如何使用以下命令通过调试符号获取参数名称ASM字节码库 http://asm.ow2.org/:

/**
 * Returns a list containing one parameter name for each argument accepted
 * by the given constructor. If the class was compiled with debugging
 * symbols, the parameter names will match those provided in the Java source
 * code. Otherwise, a generic "arg" parameter name is generated ("arg0" for
 * the first argument, "arg1" for the second...).
 * 
 * This method relies on the constructor's class loader to locate the
 * bytecode resource that defined its class.
 * 
 * @param constructor
 * @return 
 * @throws IOException
 */
public static List<String> getParameterNames(Constructor<?> constructor) throws IOException {
    Class<?> declaringClass = constructor.getDeclaringClass();
    ClassLoader declaringClassLoader = declaringClass.getClassLoader();

    Type declaringType = Type.getType(declaringClass);
    String constructorDescriptor = Type.getConstructorDescriptor(constructor);
    String url = declaringType.getInternalName() + ".class";

    InputStream classFileInputStream = declaringClassLoader.getResourceAsStream(url);
    if (classFileInputStream == null) {
        throw new IllegalArgumentException("The constructor's class loader cannot find the bytecode that defined the constructor's class (URL: " + url + ")");
    }

    ClassNode classNode;
    try {
        classNode = new ClassNode();
        ClassReader classReader = new ClassReader(classFileInputStream);
        classReader.accept(classNode, 0);
    } finally {
        classFileInputStream.close();
    }

    @SuppressWarnings("unchecked")
    List<MethodNode> methods = classNode.methods;
    for (MethodNode method : methods) {
        if (method.name.equals("<init>") && method.desc.equals(constructorDescriptor)) {
            Type[] argumentTypes = Type.getArgumentTypes(method.desc);
            List<String> parameterNames = new ArrayList<String>(argumentTypes.length);

            @SuppressWarnings("unchecked")
            List<LocalVariableNode> localVariables = method.localVariables;
            for (int i = 0; i < argumentTypes.length; i++) {
                // The first local variable actually represents the "this" object
                parameterNames.add(localVariables.get(i + 1).name);
            }

            return parameterNames;
        }
    }

    return null;
}

此示例使用 ASM 库的tree API http://asm.ow2.org/asm32/javadoc/user/org/objectweb/asm/tree/package-frame.html。如果速度和内存很宝贵，您可以重构示例以使用其访客API http://asm.ow2.org/asm32/javadoc/user/org/objectweb/asm/package-frame.html反而。