Java tutorial
/** * Copyright (c) 2005-2012 springside.org.cn * <p/> * Licensed under the Apache License, Version 2.0 (the "License"); */ package com.micmiu.mvc.ferriswheel.utils; import org.apache.commons.lang3.StringUtils; import org.apache.commons.lang3.Validate; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.ParameterizedType; import java.lang.reflect.Type; /** * ??. * <p/> * ??getter/setter, ???, ?, ?Class, AOP. */ public class ReflectionUtils { public static final String CGLIB_CLASS_SEPARATOR = "$$"; private static Logger logger = LoggerFactory.getLogger(ReflectionUtils.class); private ReflectionUtils() { } /** * Getter. */ public static Object invokeGetter(Object obj, String propertyName) { String getterMethodName = "get" + StringUtils.capitalize(propertyName); return invokeMethod(obj, getterMethodName, new Class[] {}, new Object[] {}); } /** * Setter.valueClass?Setter. */ public static void invokeSetter(Object obj, String propertyName, Object value) { invokeSetter(obj, propertyName, value, null); } /** * Setter. * * @param propertyType Setter,valueClass. */ public static void invokeSetter(Object obj, String propertyName, Object value, Class<?> propertyType) { Class<?> type = propertyType != null ? propertyType : value.getClass(); String setterMethodName = "set" + StringUtils.capitalize(propertyName); invokeMethod(obj, setterMethodName, new Class[] { type }, 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) { logger.error("??{}", e.getMessage()); } 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) { logger.error("??:{}", e.getMessage()); } } /** * cglib AOP, ?Class. */ public static Class<?> getUserClass(Class<?> clazz) { if (clazz != null && clazz.getName().contains(CGLIB_CLASS_SEPARATOR)) { Class<?> superClass = clazz.getSuperclass(); if (superClass != null && !Object.class.equals(superClass)) { return superClass; } } return clazz; } /** * , private/protected. . */ 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); } } /** * ?, ?DeclaredField, ?. * <p/> * ?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); field.setAccessible(true); return field; } catch (NoSuchFieldException e) {// NOSONAR // Field??,? } } return null; } /** * ?, ?DeclaredMethod,?. ?Object?, null. * <p/> * ?. ?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"); for (Class<?> superClass = obj.getClass(); superClass != Object.class; superClass = superClass .getSuperclass()) { try { Method method = superClass.getDeclaredMethod(methodName, parameterTypes); method.setAccessible(true); return method; } catch (NoSuchMethodException e) {// NOSONAR // Method??,? } } return null; } /** * ??, 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 */ @SuppressWarnings({ "rawtypes", "unchecked" }) public static <T> Class<T> getSuperClassGenricType(final Class clazz) { return getSuperClassGenricType(clazz, 0); } /** * ??, Class?. , Object.class. * <p/> * 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 */ @SuppressWarnings("rawtypes") public static Class getSuperClassGenricType(final Class clazz, final int index) { Type genType = clazz.getGenericSuperclass(); if (!(genType instanceof ParameterizedType)) { logger.warn(clazz.getSimpleName() + "'s superclass not ParameterizedType"); return Object.class; } Type[] params = ((ParameterizedType) genType).getActualTypeArguments(); if (index >= params.length || index < 0) { logger.warn("Index: " + index + ", Size of " + clazz.getSimpleName() + "'s Parameterized Type: " + params.length); return Object.class; } if (!(params[index] instanceof Class)) { logger.warn(clazz.getSimpleName() + " not set the actual class on superclass generic parameter"); return Object.class; } return (Class) params[index]; } /** * ??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); } /** * ?? * * @param clazz * @param index * @param <T> * @return Class<T> */ public static <T> Class<T> findParameterizedType(Class<?> clazz, int index) { Type parameterizedType = clazz.getGenericSuperclass(); //CGLUB subclass target object() if (!(parameterizedType instanceof ParameterizedType)) { parameterizedType = clazz.getSuperclass().getGenericSuperclass(); } if (!(parameterizedType instanceof ParameterizedType)) { return null; } Type[] actualTypeArguments = ((ParameterizedType) parameterizedType).getActualTypeArguments(); if (actualTypeArguments == null || actualTypeArguments.length == 0) { return null; } return (Class<T>) actualTypeArguments[index]; } }