Java tutorial
package activiti.common.persistence.util; /** * Copyright (c) 2005-2012 infosys.org.cn * * Licensed under the Apache License, Version 2.0 (the "License"); */ import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.lang.reflect.ParameterizedType; import java.lang.reflect.Type; import org.apache.commons.lang3.StringUtils; import org.apache.commons.lang3.Validate; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * ??. * * ??getter/setter, ???, ?, ?Class, AOP. * * @author free lance & updated by L.J */ public class ReflectHelper { private static final String SETTER_PREFIX = "set"; private static final String GETTER_PREFIX = "get"; private static final String CGLIB_CLASS_SEPARATOR = "$$"; /** * Getter. */ public static Object invokeGetter(Object obj, String propertyName) { String getterMethodName = GETTER_PREFIX + StringUtils.capitalize(propertyName); return invokeMethod(obj, getterMethodName, new Class[] {}, new Object[] {}); } /** * Setter, ??? */ public static void invokeSetter(Object obj, String propertyName, Object value) { String setterMethodName = SETTER_PREFIX + StringUtils.capitalize(propertyName); invokeMethodByName(obj, setterMethodName, new Object[] { value }); } /** * ?, private/protected, ??getter. */ public static Object getFieldValue(final Object obj, final String fieldName) { Field field = getAccessibleField(obj, fieldName); if (field == null) { throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + obj + "]"); } Object result = null; try { result = field.get(obj); } catch (IllegalAccessException e) { e.printStackTrace(); } return result; } /** * , private/protected, ??setter. */ public static void setFieldValue(final Object obj, final String fieldName, final Object value) { Field field = getAccessibleField(obj, fieldName); if (field == null) { throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + obj + "]"); } try { field.set(obj, value); } catch (IllegalAccessException e) { e.printStackTrace(); } } /** * , private/protected. * ?getAccessibleMethod()Method????. ????+? */ public static Object invokeMethod(final Object obj, final String methodName, final Class<?>[] parameterTypes, final Object[] args) { Method method = getAccessibleMethod(obj, methodName, parameterTypes); if (method == null) { throw new IllegalArgumentException( "Could not find method [" + methodName + "] on target [" + obj + "]"); } try { return method.invoke(obj, args); } catch (Exception e) { throw convertReflectionExceptionToUnchecked(e); } } /** * , private/protected * ?getAccessibleMethodByName()Method????. * ??????? */ public static Object invokeMethodByName(final Object obj, final String methodName, final Object[] args) { Method method = getAccessibleMethodByName(obj, methodName); if (method == null) { throw new IllegalArgumentException( "Could not find method [" + methodName + "] on target [" + obj + "]"); } try { return method.invoke(obj, args); } catch (Exception e) { throw convertReflectionExceptionToUnchecked(e); } } /** * ?, ?DeclaredField, ?. * * ?Object?, null. */ public static Field getAccessibleField(final Object obj, final String fieldName) { Validate.notNull(obj, "object can't be null"); Validate.notBlank(fieldName, "fieldName can't be blank"); for (Class<?> superClass = obj.getClass(); superClass != Object.class; superClass = superClass .getSuperclass()) { try { Field field = superClass.getDeclaredField(fieldName); makeAccessible(field); return field; } catch (NoSuchFieldException e) {// NOSONAR // Field??,? } } return null; } /** * ?, ?DeclaredMethod,?. ?Object?, null. * ???+? * * ?. ?Method,?Method.invoke(Object obj, Object... * args) */ public static Method getAccessibleMethod(final Object obj, final String methodName, final Class<?>... parameterTypes) { Validate.notNull(obj, "object can't be null"); Validate.notBlank(methodName, "methodName can't be blank"); for (Class<?> searchType = obj.getClass(); searchType != Object.class; searchType = searchType .getSuperclass()) { try { Method method = searchType.getDeclaredMethod(methodName, parameterTypes); makeAccessible(method); return method; } catch (NoSuchMethodException e) { // Method??,? } } return null; } /** * ?, ?DeclaredMethod,?. ?Object?, null. ???? * * ?. ?Method,?Method.invoke(Object obj, Object... * args) */ public static Method getAccessibleMethodByName(final Object obj, final String methodName) { Validate.notNull(obj, "object can't be null"); Validate.notBlank(methodName, "methodName can't be blank"); for (Class<?> searchType = obj.getClass(); searchType != Object.class; searchType = searchType .getSuperclass()) { Method[] methods = searchType.getDeclaredMethods(); for (Method method : methods) { if (method.getName().equals(methodName)) { makeAccessible(method); return method; } } } return null; } /** * ?private/protectedpublic?????JDKSecurityManager */ public static void makeAccessible(Method method) { if ((!Modifier.isPublic(method.getModifiers()) || !Modifier.isPublic(method.getDeclaringClass().getModifiers())) && !method.isAccessible()) { method.setAccessible(true); } } /** * ?private/protected???public?????JDKSecurityManager */ public static void makeAccessible(Field field) { if ((!Modifier.isPublic(field.getModifiers()) || !Modifier.isPublic(field.getDeclaringClass().getModifiers()) || Modifier.isFinal(field.getModifiers())) && !field.isAccessible()) { field.setAccessible(true); } } /** * ??, Class?, ? , Object.class. eg. * public UserDao extends HibernateDao<User> * * @param clazz * The class to introspect * @return the first generic declaration, or Object.class if cannot be * determined */ public static <T> Class<T> getClassGenricType(final Class clazz) { return getClassGenricType(clazz, 0); } /** * ??, Class?. , Object.class. * * public UserDao extends HibernateDao<User,Long> * * @param clazz * clazz The class to introspect * @param index * the Index of the generic ddeclaration,start from 0. * @return the index generic declaration, or Object.class if cannot be * determined */ public static Class getClassGenricType(final Class clazz, final int index) { Type genType = clazz.getGenericSuperclass(); if (!(genType instanceof ParameterizedType)) { return Object.class; } Type[] params = ((ParameterizedType) genType).getActualTypeArguments(); if ((index >= params.length) || (index < 0)) { return Object.class; } if (!(params[index] instanceof Class)) { return Object.class; } return (Class) params[index]; } public static Class<?> getUserClass(Object instance) { Validate.notNull(instance, "Instance must not be null"); Class clazz = instance.getClass(); if ((clazz != null) && clazz.getName().contains(CGLIB_CLASS_SEPARATOR)) { Class<?> superClass = clazz.getSuperclass(); if ((superClass != null) && !Object.class.equals(superClass)) { return superClass; } } return clazz; } /** * ??checked exception?unchecked exception. */ public static RuntimeException convertReflectionExceptionToUnchecked(Exception e) { if ((e instanceof IllegalAccessException) || (e instanceof IllegalArgumentException) || (e instanceof NoSuchMethodException)) { return new IllegalArgumentException(e); } else if (e instanceof InvocationTargetException) { return new RuntimeException(((InvocationTargetException) e).getTargetException()); } else if (e instanceof RuntimeException) { return (RuntimeException) e; } return new RuntimeException("Unexpected Checked Exception.", e); } /** * ?objfieldNameField * * @param obj * @param fieldName * @return */ public static Field getFieldByFieldName(Object obj, String fieldName) { if (obj == null || fieldName == null) { return null; } for (Class<?> superClass = obj.getClass(); superClass != Object.class; superClass = superClass .getSuperclass()) { try { return superClass.getDeclaredField(fieldName); } catch (Exception e) { } } return null; } /** * ?objfieldName * * @param obj * @param fieldName * @return */ public static Object getValueByFieldName(Object obj, String fieldName) { Object value = null; try { Field field = getFieldByFieldName(obj, fieldName); if (field != null) { if (field.isAccessible()) { value = field.get(obj); } else { field.setAccessible(true); value = field.get(obj); field.setAccessible(false); } } } catch (Exception e) { } return value; } /** * ?objfieldName * * @param obj * @param fieldName * @return */ @SuppressWarnings("unchecked") public static <T> T getValueByFieldType(Object obj, Class<T> fieldType) { Object value = null; for (Class<?> superClass = obj.getClass(); superClass != Object.class; superClass = superClass .getSuperclass()) { try { Field[] fields = superClass.getDeclaredFields(); for (Field f : fields) { if (f.getType() == fieldType) { if (f.isAccessible()) { value = f.get(obj); break; } else { f.setAccessible(true); value = f.get(obj); f.setAccessible(false); break; } } } if (value != null) { break; } } catch (Exception e) { } } return (T) value; } /** * objfieldName * * @param obj * @param fieldName * @param value * @throws SecurityException * @throws NoSuchFieldException * @throws IllegalArgumentException * @throws IllegalAccessException */ public static boolean setValueByFieldName(Object obj, String fieldName, Object value) { try { // java.lang.Class.getDeclaredField() - // Field??Class? // Field Field field = obj.getClass().getDeclaredField(fieldName); /** * public void setAccessible(boolean flag) throws * SecurityException accessible true * ??? Java false ?? Java * ? ReflectPermission("suppressAccessChecks") ?? * checkPermission flag true?? * Class Constructor ? SecurityException * java.lang.Class Constructor flag true? * SecurityException ? flag - accessible * SecurityException - ? */ if (field.isAccessible()) {// ? accessible field.set(obj, value);// ?? Field } else { field.setAccessible(true); field.set(obj, value); field.setAccessible(false); } return true; } catch (Exception e) { } return false; } }