java工具類——反射

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; import org.springframework.util.Assert; /** * 反射工具類. 提供調用getter/setter方法, 訪問私有變量, 調用私有方法, 獲取泛型類型Class, 被AOP過的真實類等工具函數. * * @author * @version 2019-01-15 */ @SuppressWarnings("rawtypes") public class Reflections { private static final String SETTER_PREFIX = "set"; private static final String GETTER_PREFIX = "get"; private static final String CGLIB_CLASS_SEPARATOR = "$$"; private static Logger logger = LoggerFactory.getLogger(Reflections.class); /** * 調用Getter方法. 支持多級，如：對象名.對象名.方法 */
    public static Object invokeGetter(Object obj, String propertyName) { Object object = obj; for (String name : StringUtils.split(propertyName, ".")) { String getterMethodName = GETTER_PREFIX + StringUtils.capitalize(name); object = invokeMethod(object, getterMethodName, new Class[] {}, new Object[] {}); } return object; } /** * 調用Setter方法, 僅匹配方法名。 支持多級，如：對象名.對象名.方法 */
    public static void invokeSetter(Object obj, String propertyName, Object value) { Object object = obj; String[] names = StringUtils.split(propertyName, "."); for (int i = 0; i < names.length; i++) { if (i < names.length - 1) { String getterMethodName = GETTER_PREFIX + StringUtils.capitalize(names[i]); object = invokeMethod(object, getterMethodName, new Class[] {}, new Object[] {}); } else { String setterMethodName = SETTER_PREFIX + StringUtils.capitalize(names[i]); invokeMethodByName(object, setterMethodName, new Object[] { value }); } } } /** * 直接讀取對象屬性值, 無視private/protected修飾符, 不通過getter函數. */
    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("不可能拋出的異常{}", e.getMessage()); } return result; } /** * 直接設置對象屬性值, 無視private/protected修飾符, 不通過setter函數. */
    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("不可能拋出的異常:{}", e.getMessage()); } } /** * 直接調用對象方法, 無視private/protected修飾符. * 用於一次性調用的狀況，不然應使用getAccessibleMethod()函數得到Method後反覆調用. 同時匹配方法名+參數類型， */
    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); } } /** * 直接調用對象方法, 無視private/protected修飾符， * 用於一次性調用的狀況，不然應使用getAccessibleMethodByName()函數得到Method後反覆調用. * 只匹配函數名，若是有多個同名函數調用第一個。 */
    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); } } /** * 循環向上轉型, 獲取對象的DeclaredField, 並強制設置爲可訪問. * * 如向上轉型到Object仍沒法找到, 返回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不在當前類定義,繼續向上轉型
                continue;// new add
 } } return null; } /** * 循環向上轉型, 獲取對象的DeclaredMethod,並強制設置爲可訪問. 如向上轉型到Object仍沒法找到, 返回null. * 匹配函數名+參數類型。 * * 用於方法須要被屢次調用的狀況. 先使用本函數先取得Method,而後調用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不在當前類定義,繼續向上轉型
                continue;// new add
 } } return null; } /** * 循環向上轉型, 獲取對象的DeclaredMethod,並強制設置爲可訪問. 如向上轉型到Object仍沒法找到, 返回null. 只匹配函數名。 * * 用於方法須要被屢次調用的狀況. 先使用本函數先取得Method,而後調用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; } /** * 改變private/protected的方法爲public，儘可能不調用實際改動的語句，避免JDK的SecurityManager抱怨。 */
    public static void makeAccessible(Method method) { if ((!Modifier.isPublic(method.getModifiers()) || !Modifier.isPublic(method.getDeclaringClass().getModifiers())) && !method.isAccessible()) { method.setAccessible(true); } } /** * 改變private/protected的成員變量爲public，儘可能不調用實際改動的語句，避免JDK的SecurityManager抱怨。 */
    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); } } /** * 經過反射, 得到Class定義中聲明的泛型參數的類型, 注意泛型必須定義在父類處 如沒法找到, 返回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("unchecked") public static <T> Class<T> getClassGenricType(final Class clazz) { return getClassGenricType(clazz, 0); } /** * 經過反射, 得到Class定義中聲明的父類的泛型參數的類型. 如沒法找到, 返回Object.class. * * 如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)) { 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]; } public static Class<?> getUserClass(Object instance) { Assert.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; } /** * 將反射時的checked exception轉換爲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); } }