A wrapper around reflection to resolve generics. : Generic « Reflection « Java






A wrapper around reflection to resolve generics.

   
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *    http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.GenericDeclaration;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;


/**
 * A wrapper around reflection to resolve generics.
 * 
 * @author Simone Gianni <simoneg@apache.org>
 */
// TODO there is vast space for caching and optimizations here!
public class GenericClass {

  private Class<?> myclass = null;

  private Map<String, Class<?>> genericMap = new HashMap<String, Class<?>>();

  private Map<String, String> reverseIntermediate = new HashMap<String, String>();

  public static GenericClass forClass(Class<?> concrete) {
    return new GenericClass(concrete);
  }

  public static GenericClass forField(Field field) {
    return forGenericType(field.getGenericType());
  }

  public static GenericClass forReturnType(Method method) {
    return forGenericType(method.getGenericReturnType());
  }

  public static GenericClass forParameter(Method method, int index) {
    return forGenericType(method.getGenericParameterTypes()[index]);
  }

  public static GenericClass forGenericType(Type type) {
    if (type instanceof Class) {
      return forClass((Class<?>) type);
    } else if (type instanceof ParameterizedType) {
      return new GenericClass((ParameterizedType) type);
    } else {
      return forClass(Object.class);
      // throw new MagmaException("Dont know how to build a GenericClass out of
      // {0}", type.getClass());
    }
  }

  private GenericClass(Class<?> concrete) {
    TypeVariable<?>[] parameters = concrete.getTypeParameters();
    // if (parameters.length > 0) throw new MagmaException("Cannot parse {0}, it
    // is a generic class, use a concrete class instead", concrete);
    myclass = concrete;
    recurse(concrete);
    coalesceMap();
  }

  private GenericClass(ParameterizedType type) {
    myclass = (Class<?>) type.getRawType();
    recurse(myclass, myclass, type);
    coalesceMap();
  }

  private void coalesceMap() {
    int cnt = reverseIntermediate.size();
    while (reverseIntermediate.size() > 0 && cnt > 0) {
      for (Iterator<Map.Entry<String, String>> iterator = this.reverseIntermediate.entrySet()
          .iterator(); iterator.hasNext();) {
        Map.Entry<String, String> entry = iterator.next();
        String target = entry.getValue();
        String search = entry.getKey();
        Class<?> clazz = genericMap.get(search);
        if (clazz == null)
          continue;
        if (genericMap.containsKey(target))
          throw new RuntimeException(
              "Impossible situation, it's a bug : {0} generic is both {1} and bound to {2}"
                  + target + genericMap.get(target) + search);
        genericMap.put(target, clazz);
        iterator.remove();
      }
      cnt--;
    }
    if (reverseIntermediate.size() > 0) {
      for (Iterator<Map.Entry<String, String>> iterator = this.reverseIntermediate.entrySet()
          .iterator(); iterator.hasNext();) {
        Map.Entry<String, String> entry = iterator.next();
        String target = entry.getValue();
        String search = entry.getKey();
        Class<?> clazz = genericMap.get(search);
        if (clazz == null)
          clazz = Object.class;
        if (genericMap.containsKey(target))
          throw new RuntimeException(
              "Impossible situation, it's a bug : {0} generic is both {1} and bound to {2}"+
              target+ genericMap.get(target)+ search);
        genericMap.put(target, clazz);
      }
    }
  }

  public Class<?> getBaseClass() {
    return this.myclass;
  }

  private void recurse(Class<?> clazz, Class<?> simplesup, ParameterizedType partype) {
    Type[] typeArguments = partype.getActualTypeArguments();
    TypeVariable<?>[] parameters = simplesup.getTypeParameters();

    for (int i = 0; i < typeArguments.length; i++) {
      if (typeArguments[i] instanceof Class) {
        genericMap.put(simplesup.getName() + "--" + parameters[i].getName(),
            (Class) typeArguments[i]);
      } else if (typeArguments[i] instanceof TypeVariable) {
        reverseIntermediate.put(clazz.getName() + "--"
            + ((TypeVariable<?>) typeArguments[i]).getName(), simplesup.getName() + "--"
            + parameters[i].getName());
      }
    }

    recurse(simplesup);
  }

  private void recurse(Class<?> clazz) {
    Type supclass = clazz.getGenericSuperclass();
    Class simplesup = clazz.getSuperclass();
    if (supclass == null)
      return;
    if (supclass instanceof ParameterizedType) {
      recurse(clazz, simplesup, (ParameterizedType) supclass);
    } else {
      recurse(simplesup);
    }
  }

  /**
   * Return real, "generics dereferenced", parameter types for the given method.
   * 
   * @param method
   *          The method to analyze
   * @return The real classes, dereferencing generics
   */
  public GenericClass[] getParameterTypes(Method method) {
    Class<?> declaring = method.getDeclaringClass();
    String declname = declaring.getName();

    Type[] parameterTypes = method.getGenericParameterTypes();
    GenericClass[] ret = new GenericClass[parameterTypes.length];
    for (int i = 0; i < parameterTypes.length; i++) {
      Type type = parameterTypes[i];
      if (type instanceof Class) {
        ret[i] = forClass((Class<?>) type);
      } else if (type instanceof TypeVariable) {
        String name = ((TypeVariable<?>) type).getName();
        Class<?> sub = genericMap.get(declname + "--" + name);
        if (sub == null)
          sub = Object.class;
        ret[i] = forClass(sub);
      } else {
        ret[i] = forGenericType(type);
      }
    }
    return ret;
  }

  public GenericClass resolveType(Type type) {
    if (type instanceof Class) {
      return forClass((Class<?>) type);
    } else if (type instanceof TypeVariable) {
      GenericDeclaration gd = ((TypeVariable<?>) type).getGenericDeclaration();
      Class<?> acclass = null;
      if (gd instanceof Class) {
        acclass = (Class<?>) gd;
      } else if (gd instanceof Method) {
        acclass = ((Method) gd).getDeclaringClass();
      } else if (gd instanceof Constructor) {
        acclass = ((Constructor<?>) gd).getDeclaringClass();
      }
      String name = ((TypeVariable<?>) type).getName();
      return forClass(genericMap.get(acclass.getName() + "--" + name));
    } else {
      return forGenericType(type);
    }
  }

  /**
   * Search for all occurrencies of a specific method.
   * <p>
   * The type parameters passed in may be Class or null. If they are null, that
   * means that we don't know which class they should be, if they are a class,
   * that means we are searching for that class, and the comparison is made on
   * dereferenced generics.
   * </p>
   * <p>
   * Specifying no parameter types explicitly means "a method without
   * parameters".
   * </p>
   * 
   * @param name
   *          The name of the method
   * @param parameterTypes
   *          The types of the parameters
   * @return A list of {@link MethodDef}, ordered with methods from current
   *         class first, then method from superclass and so on.
   */
  public List<MethodDef> findMethods(String name, Class<?>... parameterTypes) {
    List<MethodDef> founds = new ArrayList<MethodDef>();
    Class<?> current = myclass;
    while (current != null) {
      Method[] methods = current.getDeclaredMethods();
      for (Method method : methods) {
        if (!method.isBridge() && !method.isSynthetic() && method.getName().equals(name)) {
          Type[] types = method.getGenericParameterTypes();
          if (types.length == parameterTypes.length) {
            GenericClass[] genericClasses = getParameterTypes(method);
            Class<?>[] classes = toRawClasses(genericClasses);
            boolean good = true;
            for (int i = 0; i < types.length; i++) {
              if (parameterTypes[i] != null) {
                if (!classes[i].equals(parameterTypes[i])) {
                  good = false;
                  break;
                }
              }
            }
            if (good) {
              MethodDef def = new MethodDef(method, genericClasses);
              if (!founds.contains(def))
                founds.add(def);
            }
          }
        }
      }
      current = current.getSuperclass();
    }
    return founds;
  }

  public static Class<?>[] toRawClasses(GenericClass[] genclasses) {
    Class<?>[] ret = new Class<?>[genclasses.length];
    for (int i = 0; i < genclasses.length; i++) {
      ret[i] = genclasses[i].getBaseClass();
    }
    return ret;
  }

  /**
   * Search for all methods having that name, no matter which parameter they
   * take.
   * 
   * @param name
   *          The name of the methods
   * @return A list of {@link MethodDef}, ordered with methods from current
   *         class first, then method from superclass and so on.
   */
  public List<MethodDef> findAllMethods(String name) {
    List<MethodDef> founds = new ArrayList<MethodDef>();
    Class<?> current = myclass;
    while (current != null) {
      Method[] methods = current.getDeclaredMethods();
      for (Method method : methods) {
        if (!method.isBridge() && !method.isSynthetic() && method.getName().equals(name)) {
          MethodDef def = new MethodDef(method);
          if (!founds.contains(def))
            founds.add(def);
        }
      }
      current = current.getSuperclass();
    }
    return founds;
  }

  public List<MethodDef> getMethods() {
    List<MethodDef> founds = new ArrayList<MethodDef>();
    Class<?> current = myclass;
    while (current != null) {
      Method[] methods = current.getDeclaredMethods();
      for (Method method : methods) {
        if (!method.isBridge() && !method.isSynthetic()) {
          MethodDef def = new MethodDef(method);
          if (!founds.contains(def))
            founds.add(def);
        }
      }
      current = current.getSuperclass();
    }
    return founds;
  }

  @Override
  public boolean equals(Object obj) {
    if (!(obj instanceof GenericClass))
      return false;
    GenericClass oth = (GenericClass) obj;
    return this.getBaseClass().equals(oth.getBaseClass());
  }

  public class MethodDef {
    private Method method = null;

    private GenericClass[] params = null;

    MethodDef(Method m) {
      this.method = m;
    }

    MethodDef(Method m, GenericClass[] params) {
      this.method = m;
      this.params = params;
    }

    public String getName() {
      return this.method.getName();
    }

    public Method getBaseMethod() {
      return this.method;
    }

    public GenericClass[] getParameterTypes() {
      if (this.params == null) {
        this.params = GenericClass.this.getParameterTypes(method);
      }
      return this.params;
    }

    public GenericClass getReturnType() {
      return resolveType(method.getGenericReturnType());
    }

    @Override
    public boolean equals(Object other) {
      if (!(other instanceof MethodDef))
        return false;
      MethodDef oth = (MethodDef) other;
      return (method.getName().equals(oth.method.getName()))
          && (Arrays.equals(getParameterTypes(), oth.getParameterTypes()));
    }

    public Class<?> getDeclaringClass() {
      return this.method.getDeclaringClass();
    }
  }

}

   
    
    
  








Related examples in the same category

1.Get Generic Super class
2.Generic Class reflection
3.Get field type and generic type by field name
4.get Return Type and get Generic Return Type
5.get Exception Types and get Generic Exception Types
6.get Parameter Types and get Generic ParameterTypes
7.Generic method reflection
8.get Generic Parameter Types from Constructor
9.Class Declaration Spy
10.All information about a class
11.Get all implemented generic interfaces
12.If right-hand side type may be assigned to the left-hand side type following the Java generics rules.
13.Get all interface and object classes that are generalizations of the provided class
14.Get Generic Type
15.Get Parameterized Type
16.Locates generic declaration by index on a class.