Find method : Method « Reflection « Java Tutorial

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//
//$Id: IntrospectionUtil.java 1540 2007-01-19 12:24:10Z janb $
//Copyright 2006 Mort Bay Consulting Pty. Ltd.
//------------------------------------------------------------------------
//Licensed 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.Field;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.List;

public class IntrospectionUtil {
  public static Method findMethod(Class clazz, String methodName, Class[] args,
      boolean checkInheritance, boolean strictArgs) throws NoSuchMethodException {
    if (clazz == null)
      throw new NoSuchMethodException("No class");
    if (methodName == null || methodName.trim().equals(""))
      throw new NoSuchMethodException("No method name");

    Method method = null;
    Method[] methods = clazz.getDeclaredMethods();
    for (int i = 0; i < methods.length && method == null; i++) {
      if (methods[i].getName().equals(methodName)
          && checkParams(methods[i].getParameterTypes(), (args == null ? new Class[] {} : args),
              strictArgs)) {
        method = methods[i];
      }

    }
    if (method != null) {
      return method;
    } else if (checkInheritance)
      return findInheritedMethod(clazz.getPackage(), clazz.getSuperclass(), methodName, args,
          strictArgs);
    else
      throw new NoSuchMethodException("No such method " + methodName + " on class "
          + clazz.getName());

  }

  public static Field findField(Class clazz, String targetName, Class targetType,
      boolean checkInheritance, boolean strictType) throws NoSuchFieldException {
    if (clazz == null)
      throw new NoSuchFieldException("No class");
    if (targetName == null)
      throw new NoSuchFieldException("No field name");

    try {
      Field field = clazz.getDeclaredField(targetName);
      if (strictType) {
        if (field.getType().equals(targetType))
          return field;
      } else {
        if (field.getType().isAssignableFrom(targetType))
          return field;
      }
      if (checkInheritance) {
        return findInheritedField(clazz.getPackage(), clazz.getSuperclass(), targetName,
            targetType, strictType);
      } else
        throw new NoSuchFieldException("No field with name " + targetName + " in class "
            + clazz.getName() + " of type " + targetType);
    } catch (NoSuchFieldException e) {
      return findInheritedField(clazz.getPackage(), clazz.getSuperclass(), targetName, targetType,
          strictType);
    }
  }

  public static boolean isInheritable(Package pack, Member member) {
    if (pack == null)
      return false;
    if (member == null)
      return false;

    int modifiers = member.getModifiers();
    if (Modifier.isPublic(modifiers))
      return true;
    if (Modifier.isProtected(modifiers))
      return true;
    if (!Modifier.isPrivate(modifiers) && pack.equals(member.getDeclaringClass().getPackage()))
      return true;

    return false;
  }

  public static boolean checkParams(Class[] formalParams, Class[] actualParams, boolean strict) {
    if (formalParams == null && actualParams == null)
      return true;
    if (formalParams == null && actualParams != null)
      return false;
    if (formalParams != null && actualParams == null)
      return false;

    if (formalParams.length != actualParams.length)
      return false;

    if (formalParams.length == 0)
      return true;

    int j = 0;
    if (strict) {
      while (j < formalParams.length && formalParams[j].equals(actualParams[j]))
        j++;
    } else {
      while ((j < formalParams.length) && (formalParams[j].isAssignableFrom(actualParams[j]))) {
        j++;
      }
    }

    if (j != formalParams.length) {
      return false;
    }

    return true;
  }

  public static boolean isSameSignature(Method methodA, Method methodB) {
    if (methodA == null)
      return false;
    if (methodB == null)
      return false;

    List parameterTypesA = Arrays.asList(methodA.getParameterTypes());
    List parameterTypesB = Arrays.asList(methodB.getParameterTypes());

    if (methodA.getName().equals(methodB.getName()) && parameterTypesA.containsAll(parameterTypesB))
      return true;

    return false;
  }

  public static boolean isTypeCompatible(Class formalType, Class actualType, boolean strict) {
    if (formalType == null && actualType != null)
      return false;
    if (formalType != null && actualType == null)
      return false;
    if (formalType == null && actualType == null)
      return true;

    if (strict)
      return formalType.equals(actualType);
    else
      return formalType.isAssignableFrom(actualType);
  }

  public static boolean containsSameMethodSignature(Method method, Class c, boolean checkPackage) {
    if (checkPackage) {
      if (!c.getPackage().equals(method.getDeclaringClass().getPackage()))
        return false;
    }

    boolean samesig = false;
    Method[] methods = c.getDeclaredMethods();
    for (int i = 0; i < methods.length && !samesig; i++) {
      if (IntrospectionUtil.isSameSignature(method, methods[i]))
        samesig = true;
    }
    return samesig;
  }

  public static boolean containsSameFieldName(Field field, Class c, boolean checkPackage) {
    if (checkPackage) {
      if (!c.getPackage().equals(field.getDeclaringClass().getPackage()))
        return false;
    }

    boolean sameName = false;
    Field[] fields = c.getDeclaredFields();
    for (int i = 0; i < fields.length && !sameName; i++) {
      if (fields[i].getName().equals(field.getName()))
        sameName = true;
    }
    return sameName;
  }

  protected static Method findInheritedMethod(Package pack, Class clazz, String methodName,
      Class[] args, boolean strictArgs) throws NoSuchMethodException {
    if (clazz == null)
      throw new NoSuchMethodException("No class");
    if (methodName == null)
      throw new NoSuchMethodException("No method name");

    Method method = null;
    Method[] methods = clazz.getDeclaredMethods();
    for (int i = 0; i < methods.length && method == null; i++) {
      if (methods[i].getName().equals(methodName) && isInheritable(pack, methods[i])
          && checkParams(methods[i].getParameterTypes(), args, strictArgs))
        method = methods[i];
    }
    if (method != null) {
      return method;
    } else
      return findInheritedMethod(clazz.getPackage(), clazz.getSuperclass(), methodName, args,
          strictArgs);
  }

  protected static Field findInheritedField(Package pack, Class clazz, String fieldName,
      Class fieldType, boolean strictType) throws NoSuchFieldException {
    if (clazz == null)
      throw new NoSuchFieldException("No class");
    if (fieldName == null)
      throw new NoSuchFieldException("No field name");
    try {
      Field field = clazz.getDeclaredField(fieldName);
      if (isInheritable(pack, field) && isTypeCompatible(fieldType, field.getType(), strictType))
        return field;
      else
        return findInheritedField(clazz.getPackage(), clazz.getSuperclass(), fieldName, fieldType,
            strictType);
    } catch (NoSuchFieldException e) {
      return findInheritedField(clazz.getPackage(), clazz.getSuperclass(), fieldName, fieldType,
          strictType);
    }
  }

}