Spring 中一个常用的反射类库ReflectionUtils

 

在项目中部分方法采用反射，通过类访问类的属性，通过类反问方法，通过属性访问方法。以及常用异常的处理在等可以使用反射出处理。

 

public abstract class ReflectionUtils {

 

 /**根据类和属性名称查找属性字段
  * Attempt to find a {@link Field field} on the supplied {@link Class} with
  * the supplied <code>name</code>. Searches all superclasses up to {@link Object}.
  * @param clazz the class to introspect
  * @param name the name of the field
  * @return the corresponding Field object, or <code>null</code> if not found
  */
 public static Field findField(Class clazz, String name) {
  return findField(clazz, name, null);
 }

 

 /**根据类和属性名称查找属性字段
  * Attempt to find a {@link Field field} on the supplied {@link Class} with
  * the supplied <code>name</code> and/or {@link Class type}. Searches all
  * superclasses up to {@link Object}.
  * @param clazz the class to introspect
  * @param name the name of the field (may be <code>null</code> if type is specified)
  * @param type the type of the field (may be <code>null</code> if name is specified)
  * @return the corresponding Field object, or <code>null</code> if not found
  */
 public static Field findField(Class clazz, String name, Class type) {
  Assert.notNull(clazz, "Class must not be null");
  Assert.isTrue(name != null || type != null, "Either name or type of the field must be specified");
  Class searchType = clazz;
  while (!Object.class.equals(searchType) && searchType != null) {
   Field[] fields = searchType.getDeclaredFields();
   for (int i = 0; i < fields.length; i++) {
    Field field = fields[i];
    if ((name == null || name.equals(field.getName()))
      && (type == null || type.equals(field.getType()))) {
     return field;
    }
   }
   searchType = searchType.getSuperclass();
  }
  return null;
 }

 

 /**根据属性字段和对象，设置对象的值
  * Set the field represented by the supplied {@link Field field object} on
  * the specified {@link Object target object} to the specified
  * <code>value</code>. In accordance with
  * {@link Field#set(Object, Object)} semantics, the new value is
  * automatically unwrapped if the underlying field has a primitive type.
  * <p>Thrown exceptions are handled via a call to
  * {@link #handleReflectionException(Exception)}.
  * @param field the field to set
  * @param target the target object on which to set the field
  * @param value the value to set; may be <code>null</code>
  */
 public static void setField(Field field, Object target, Object value) {
  try {
   field.set(target, value);
  }
  catch (IllegalAccessException ex) {
   handleReflectionException(ex);
   throw new IllegalStateException(
     "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
  }
 }

 

 /**根据属性字段和对象，获取的对象中字段的值
  * Get the field represented by the supplied {@link Field field object} on
  * the specified {@link Object target object}. In accordance with
  * {@link Field#get(Object)} semantics, the returned value is
  * automatically wrapped if the underlying field has a primitive type.
  * <p>Thrown exceptions are handled via a call to
  * {@link #handleReflectionException(Exception)}.
  * @param field the field to get
  * @param target the target object from which to get the field
  * @return the field's current value
  */
 public static Object getField(Field field, Object target) {
  try {
   return field.get(target);
  }
  catch (IllegalAccessException ex) {
   handleReflectionException(ex);
   throw new IllegalStateException(
     "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
  }
 }

 

 /**根据类，方法名称和参数类型查找方法
  * Attempt to find a {@link Method} on the supplied class with the supplied name
  * and no parameters. Searches all superclasses up to <code>Object</code>.
  * <p>Returns <code>null</code> if no {@link Method} can be found.
  * @param clazz the class to introspect
  * @param name the name of the method
  * @return the Method object, or <code>null</code> if none found
  */
 public static Method findMethod(Class clazz, String name) {
  return findMethod(clazz, name, new Class[0]);
 }

 

 /**根据类，方法名称和参数类型查找方法
  * Attempt to find a {@link Method} on the supplied class with the supplied name
  * and parameter types. Searches all superclasses up to <code>Object</code>.
  * <p>Returns <code>null</code> if no {@link Method} can be found.
  * @param clazz the class to introspect
  * @param name the name of the method
  * @param paramTypes the parameter types of the method
  * (may be <code>null</code> to indicate any signature)
  * @return the Method object, or <code>null</code> if none found
  */
 public static Method findMethod(Class clazz, String name, Class[] paramTypes) {
  Assert.notNull(clazz, "Class must not be null");
  Assert.notNull(name, "Method name must not be null");
  Class searchType = clazz;
  while (!Object.class.equals(searchType) && searchType != null) {
   Method[] methods = (searchType.isInterface() ? searchType.getMethods() : searchType.getDeclaredMethods());
   for (int i = 0; i < methods.length; i++) {
    Method method = methods[i];
    if (name.equals(method.getName()) &&
      (paramTypes == null || Arrays.equals(paramTypes, method.getParameterTypes()))) {
     return method;
    }
   }
   searchType = searchType.getSuperclass();
  }
  return null;
 }

 

 

 /**调用方法的应用
  * Invoke the specified {@link Method} against the supplied target object
  * with no arguments. The target object can be <code>null</code> when
  * invoking a static {@link Method}.
  * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
  * @param method the method to invoke
  * @param target the target object to invoke the method on
  * @return the invocation result, if any
  * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
  */
 public static Object invokeMethod(Method method, Object target) {
  return invokeMethod(method, target, null);
 }

 

 /**调用方法的应用
  * Invoke the specified {@link Method} against the supplied target object
  * with the supplied arguments. The target object can be <code>null</code>
  * when invoking a static {@link Method}.
  * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
  * @param method the method to invoke
  * @param target the target object to invoke the method on
  * @param args the invocation arguments (may be <code>null</code>)
  * @return the invocation result, if any
  */
 public static Object invokeMethod(Method method, Object target, Object[] args) {
  try {
   return method.invoke(target, args);
  }
  catch (Exception ex) {
   handleReflectionException(ex);
  }
  throw new IllegalStateException("Should never get here");
 }

 

 /**
  * Invoke the specified JDBC API {@link Method} against the supplied
  * target object with no arguments.
  * @param method the method to invoke
  * @param target the target object to invoke the method on
  * @return the invocation result, if any
  * @throws SQLException the JDBC API SQLException to rethrow (if any)
  * @see #invokeJdbcMethod(java.lang.reflect.Method, Object, Object[])
  */
 public static Object invokeJdbcMethod(Method method, Object target) throws SQLException {
  return invokeJdbcMethod(method, target, null);
 }

 /**
  * Invoke the specified JDBC API {@link Method} against the supplied
  * target object with the supplied arguments.
  * @param method the method to invoke
  * @param target the target object to invoke the method on
  * @param args the invocation arguments (may be <code>null</code>)
  * @return the invocation result, if any
  * @throws SQLException the JDBC API SQLException to rethrow (if any)
  * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
  */
 public static Object invokeJdbcMethod(Method method, Object target, Object[] args) throws SQLException {
  try {
   return method.invoke(target, args);
  }
  catch (IllegalAccessException ex) {
   handleReflectionException(ex);
  }
  catch (InvocationTargetException ex) {
   if (ex.getTargetException() instanceof SQLException) {
    throw (SQLException) ex.getTargetException();
   }
   handleInvocationTargetException(ex);
  }
  throw new IllegalStateException("Should never get here");
 }

 

/**************************************************************

*

* 处理异常的方法

*

***************************************************************/

 

/** 使用反射处理异常的将异常信息输出但不抛出方法以外
  * Handle the given reflection exception. Should only be called if
  * no checked exception is expected to be thrown by the target method.
  * <p>Throws the underlying RuntimeException or Error in case of an
  * InvocationTargetException with such a root cause. Throws an
  * IllegalStateException with an appropriate message else.
  * @param ex the reflection exception to handle
  */
 public static void handleReflectionException(Exception ex) {
  if (ex instanceof NoSuchMethodException) {
   throw new IllegalStateException("Method not found: " + ex.getMessage());
  }
  if (ex instanceof IllegalAccessException) {
   throw new IllegalStateException("Could not access method: " + ex.getMessage());
  }
  if (ex instanceof InvocationTargetException) {
   handleInvocationTargetException((InvocationTargetException) ex);
  }
  if (ex instanceof RuntimeException) {
   throw (RuntimeException) ex;
  }
  handleUnexpectedException(ex);
 }

 

 

 /** 
  * Handle the given invocation target exception. Should only be called if
  * no checked exception is expected to be thrown by the target method.
  * <p>Throws the underlying RuntimeException or Error in case of such
  * a root cause. Throws an IllegalStateException else.
  * @param ex the invocation target exception to handle
  */
 public static void handleInvocationTargetException(InvocationTargetException ex) {
  rethrowRuntimeException(ex.getTargetException());
 }

 

 /**
  * Rethrow the given {@link Throwable exception}, which is presumably the
  * <em>target exception</em> of an {@link InvocationTargetException}.
  * Should only be called if no checked exception is expected to be thrown by
  * the target method.
  * <p>Rethrows the underlying exception cast to an {@link RuntimeException}
  * or {@link Error} if appropriate; otherwise, throws an
  * {@link IllegalStateException}.
  * @param ex the exception to rethrow
  * @throws RuntimeException the rethrown exception
  */
 public static void rethrowRuntimeException(Throwable ex) {
  if (ex instanceof RuntimeException) {
   throw (RuntimeException) ex;
  }
  if (ex instanceof Error) {
   throw (Error) ex;
  }
  handleUnexpectedException(ex);
 }

 /**
  * Rethrow the given {@link Throwable exception}, which is presumably the
  * <em>target exception</em> of an {@link InvocationTargetException}.
  * Should only be called if no checked exception is expected to be thrown by
  * the target method.
  * <p>Rethrows the underlying exception cast to an {@link Exception} or
  * {@link Error} if appropriate; otherwise, throws an
  * {@link IllegalStateException}.
  * @param ex the exception to rethrow
  * @throws Exception the rethrown exception (in case of a checked exception)
  */
 public static void rethrowException(Throwable ex) throws Exception {
  if (ex instanceof Exception) {
   throw (Exception) ex;
  }
  if (ex instanceof Error) {
   throw (Error) ex;
  }
  handleUnexpectedException(ex);
 }

 /**
  * Throws an IllegalStateException with the given exception as root cause.
  * @param ex the unexpected exception
  */
 private static void handleUnexpectedException(Throwable ex) {
  // Needs to avoid the chained constructor for JDK 1.4 compatibility.
  IllegalStateException isex = new IllegalStateException("Unexpected exception thrown");
  isex.initCause(ex);
  throw isex;
 }

 

 

 

 

 /**
  * Determine whether the given method explicitly declares the given exception
  * or one of its superclasses, which means that an exception of that type
  * can be propagated as-is within a reflective invocation.
  * @param method the declaring method
  * @param exceptionType the exception to throw
  * @return <code>true</code> if the exception can be thrown as-is;
  * <code>false</code> if it needs to be wrapped
  */
 public static boolean declaresException(Method method, Class exceptionType) {
  Assert.notNull(method, "Method must not be null");
  Class[] declaredExceptions = method.getExceptionTypes();
  for (int i = 0; i < declaredExceptions.length; i++) {
   Class declaredException = declaredExceptions[i];
   if (declaredException.isAssignableFrom(exceptionType)) {
    return true;
   }
  }
  return false;
 }

 

/*************************************************************

*

*

*  判断方法，属性字段等的修饰符的方法

*************************************************************/
 /**
  * Determine whether the given field is a "public static final" constant.
  * @param field the field to check
  */
 public static boolean isPublicStaticFinal(Field field) {
  int modifiers = field.getModifiers();
  return (Modifier.isPublic(modifiers) && Modifier.isStatic(modifiers) && Modifier.isFinal(modifiers));
 }

 /**
  * Determine whether the given method is an "equals" method.
  * @see java.lang.Object#equals
  */
 public static boolean isEqualsMethod(Method method) {
  if (method == null || !method.getName().equals("equals")) {
   return false;
  }
  Class[] paramTypes = method.getParameterTypes();
  return (paramTypes.length == 1 && paramTypes[0] == Object.class);
 }

 /**
  * Determine whether the given method is a "hashCode" method.
  * @see java.lang.Object#hashCode
  */
 public static boolean isHashCodeMethod(Method method) {
  return (method != null && method.getName().equals("hashCode") &&
    method.getParameterTypes().length == 0);
 }

 /**
  * Determine whether the given method is a "toString" method.
  * @see java.lang.Object#toString()
  */
 public static boolean isToStringMethod(Method method) {
  return (method != null && method.getName().equals("toString") &&
    method.getParameterTypes().length == 0);
 }

 

 

 /**  判断一个属性是否可以访问的方法 
  * Make the given field accessible, explicitly setting it accessible if necessary.
  * The <code>setAccessible(true)</code> method is only called when actually necessary,
  * to avoid unnecessary conflicts with a JVM SecurityManager (if active).
  * @param field the field to make accessible
  * @see java.lang.reflect.Field#setAccessible
  */
 public static void makeAccessible(Field field) {
  if (!Modifier.isPublic(field.getModifiers()) ||
    !Modifier.isPublic(field.getDeclaringClass().getModifiers())) {
   field.setAccessible(true);
  }
 }

 

 /**  判断一个方法是否可以访问的方法  
  * Make the given method accessible, explicitly setting it accessible if necessary.
  * The <code>setAccessible(true)</code> method is only called when actually necessary,
  * to avoid unnecessary conflicts with a JVM SecurityManager (if active).
  * @param method the method to make accessible
  * @see java.lang.reflect.Method#setAccessible
  */
 public static void makeAccessible(Method method) {
  if (!Modifier.isPublic(method.getModifiers()) ||
    !Modifier.isPublic(method.getDeclaringClass().getModifiers())) {
   method.setAccessible(true);
  }
 }

 

 /**  判断一个构造函数是否可以访问的方法  
  * Make the given constructor accessible, explicitly setting it accessible if necessary.
  * The <code>setAccessible(true)</code> method is only called when actually necessary,
  * to avoid unnecessary conflicts with a JVM SecurityManager (if active).
  * @param ctor the constructor to make accessible
  * @see java.lang.reflect.Constructor#setAccessible
  */
 public static void makeAccessible(Constructor ctor) {
  if (!Modifier.isPublic(ctor.getModifiers()) ||
    !Modifier.isPublic(ctor.getDeclaringClass().getModifiers())) {
   ctor.setAccessible(true);
  }
 }

 /**
  * Perform the given callback operation on all matching methods of the
  * given class and superclasses.
  * <p>The same named method occurring on subclass and superclass will
  * appear twice, unless excluded by a {@link MethodFilter}.
  * @param targetClass class to start looking at
  * @param mc the callback to invoke for each method
  * @see #doWithMethods(Class, MethodCallback, MethodFilter)
  */
 public static void doWithMethods(Class targetClass, MethodCallback mc) throws IllegalArgumentException {
  doWithMethods(targetClass, mc, null);
 }

 

 

 /**
  * Perform the given callback operation on all matching methods of the
  * given class and superclasses.
  * <p>The same named method occurring on subclass and superclass will
  * appear twice, unless excluded by the specified {@link MethodFilter}.
  * @param targetClass class to start looking at
  * @param mc the callback to invoke for each method
  * @param mf the filter that determines the methods to apply the callback to
  */
 public static void doWithMethods(Class targetClass, MethodCallback mc, MethodFilter mf)
   throws IllegalArgumentException {

  // Keep backing up the inheritance hierarchy.
  do {
   Method[] methods = targetClass.getDeclaredMethods();
   for (int i = 0; i < methods.length; i++) {
    if (mf != null && !mf.matches(methods[i])) {
     continue;
    }
    try {
     mc.doWith(methods[i]);
    }
    catch (IllegalAccessException ex) {
     throw new IllegalStateException(
       "Shouldn't be illegal to access method '" + methods[i].getName() + "': " + ex);
    }
   }
   targetClass = targetClass.getSuperclass();
  }
  while (targetClass != null);
 }

 

/**获取类的所有的方法的
  * Get all declared methods on the leaf class and all superclasses.
  * Leaf class methods are included first.
  */
 public static Method[] getAllDeclaredMethods(Class leafClass) throws IllegalArgumentException {
  final List list = new ArrayList(32);
  doWithMethods(leafClass, new MethodCallback() {
   public void doWith(Method method) {
    list.add(method);
   }
  });
  return (Method[]) list.toArray(new Method[list.size()]);
 }

 

 /**调用字段时执行的回调的方法
  * Invoke the given callback on all fields in the target class,
  * going up the class hierarchy to get all declared fields.
  * @param targetClass the target class to analyze
  * @param fc the callback to invoke for each field
  */
 public static void doWithFields(Class targetClass, FieldCallback fc) throws IllegalArgumentException {
  doWithFields(targetClass, fc, null);
 }

 

 /**调用字段时执行的回调的并过滤的方法
  * Invoke the given callback on all fields in the target class,
  * going up the class hierarchy to get all declared fields.
  * @param targetClass the target class to analyze
  * @param fc the callback to invoke for each field
  * @param ff the filter that determines the fields to apply the callback to
  */
 public static void doWithFields(Class targetClass, FieldCallback fc, FieldFilter ff)
   throws IllegalArgumentException {

  // Keep backing up the inheritance hierarchy.
  do {
   // Copy each field declared on this class unless it's static or file.
   Field[] fields = targetClass.getDeclaredFields();
   for (int i = 0; i < fields.length; i++) {
    // Skip static and final fields.
    if (ff != null && !ff.matches(fields[i])) {
     continue;
    }
    try {
     fc.doWith(fields[i]);
    }
    catch (IllegalAccessException ex) {
     throw new IllegalStateException(
       "Shouldn't be illegal to access field '" + fields[i].getName() + "': " + ex);
    }
   }
   targetClass = targetClass.getSuperclass();
  }
  while (targetClass != null && targetClass != Object.class);
 }

 

 

 /**用于对象的拷贝的方法（类必须是同一类或子类）
  * Given the source object and the destination, which must be the same class
  * or a subclass, copy all fields, including inherited fields. Designed to
  * work on objects with public no-arg constructors.
  * @throws IllegalArgumentException if the arguments are incompatible
  */
 public static void shallowCopyFieldState(final Object src, final Object dest) throws IllegalArgumentException {
  if (src == null) {
   throw new IllegalArgumentException("Source for field copy cannot be null");
  }
  if (dest == null) {
   throw new IllegalArgumentException("Destination for field copy cannot be null");
  }
  if (!src.getClass().isAssignableFrom(dest.getClass())) {
   throw new IllegalArgumentException("Destination class [" + dest.getClass().getName() +
     "] must be same or subclass as source class [" + src.getClass().getName() + "]");
  }

  doWithFields(src.getClass(), new FieldCallback() {
   public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException {
    makeAccessible(field);
    Object srcValue = field.get(src);
    field.set(dest, srcValue);
   }
  }, COPYABLE_FIELDS);
 }

 

 /**
  * Action to take on each method.
  */
 public static interface MethodCallback {

  /**
   * Perform an operation using the given method.
   * @param method the method to operate on
   */
  void doWith(Method method) throws IllegalArgumentException, IllegalAccessException;
 }

 /**
  * Callback optionally used to method fields to be operated on by a method callback.
  */
 public static interface MethodFilter {

  /**
   * Determine whether the given method matches.
   * @param method the method to check
   */
  boolean matches(Method method);
 }

 /**
  * Callback interface invoked on each field in the hierarchy.
  */
 public static interface FieldCallback {

  /**
   * Perform an operation using the given field.
   * @param field the field to operate on
   */
  void doWith(Field field) throws IllegalArgumentException, IllegalAccessException;
 }

 /**
  * Callback optionally used to filter fields to be operated on by a field callback.
  */
 public static interface FieldFilter {

  /**
   * Determine whether the given field matches.
   * @param field the field to check
   */
  boolean matches(Field field);
 }

 /**
  * Pre-built FieldFilter that matches all non-static, non-final fields.
  */
 public static FieldFilter COPYABLE_FIELDS = new FieldFilter() {
  public boolean matches(Field field) {
   return !(Modifier.isStatic(field.getModifiers()) ||
     Modifier.isFinal(field.getModifiers()));
  }
 };

}