反射机制
反射机制可通过在运行时加载类名而获取类，并对其进行操作。工厂模式，动态代理中较常用到。
在实际场景中：由于有好多类具有共同的接口样式，而他们又用的不是很频繁，如果在服务器中保有这些类会占用资源空间，如果通过接口指定的方式去加载，用完之后就销毁掉，可节省资源空间，且实现接口编程，扩展性好，代码量也少。打个比方：哺乳动物Animal为接口，里面包括获取乳头数，获取腿，获取头，获取尾巴等，像这种都具有一定共性，实现类为老虎，狮子，兔子，羊等等等。
1.获取className,常用的形式将需要反射的类放在属性文件*.properties或数据库字段中，通过key获取类名及路径。
1 private static final String CLASS_NAME_PATH = "pattern/classname.properties";
2
3 /**
4 * 获取类名称
5 * @return
6 */
7 private static String getClassName(String name) {
8 Properties pro = new Properties();
9 try {
10 String url = ProxyFactory.class.getClassLoader().getResource("").getPath() + CLASS_NAME_PATH;
11 pro.load(new FileInputStream(url));
12 } catch (FileNotFoundException e) {
13 e.printStackTrace();
14 } catch (IOException e) {
15 e.printStackTrace();
16 }
17 return (String)pro.get(name);
18 }
getClassName
1 # animal 2 lion = pattern.creation.factory.animal.Lion 3 sheep = pattern.creation.factory.animal.Sheep 4 rabit = pattern.creation.factory.animal.Rabit 5 # plant 6 apple = pattern.creation.factory.plant.Apple 7 pear = pattern.creation.factory.plant.Pear 8 plum = pattern.creation.factory.plant.Plum
classPath.properties
>>> String strClass = getClassName("rabit");//获取兔子类
2.获取类，创建类实例
Class<?> clazz = Class.forName(strClass); //获取类
Object obj = clazz.newInstance()； //构建实例对象
Class<?> superClazz = clazz.getSuperclass(); //获取父类
Class<?>[] interfaceArray = clazz.getInterfaces();//获取接口
1 /**
2 * 根据classname获取类名
3 * @param strName
4 * @return
5 * @throws ClassNotFoundException
6 * @throws InstantiationException
7 * @throws IllegalAccessException
8 */
9 @SuppressWarnings("unchecked")
10 public <T> T getClassByName(String strName) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
11 String strClass = getClassName(strName);
12 Class<?> clazz = Class.forName(strClass);
13 Class<?> superClazz = clazz.getSuperclass();
14 Class<?>[] interfaceArray = clazz.getInterfaces();
15 System.out.println("className--: " + clazz.getName());//当前类名
16 System.out.println("superClassName--: " + superClazz.getName());//父类
17 for(Class<?> interfaces: interfaceArray){
18 System.out.println("interface--: " + interfaces.getName());//接口
19 }
20 return (T)clazz.newInstance();
21 }
getClass
>>> AnimalFactory animal = reflectFactory.getClassByName("rabit");
运行结果：
className--: pattern.creation.factory.animal.Rabit
superClassName--: pattern.creation.factory.animal.Animals
interface--: pattern.creation.factory.animal.AnimalFactory
3. 获取类属性及信息
Field[] fieldArray = clazz.getDeclaredFields(); // 显示所有的属性
Field[] publicFieldArray = clazz.getFields(); //显示public属性的元素
String name = field.getName(); //获取方法名
String modify = Modifier.toString(field.getModifiers()); // 修饰词
String classType = field.getType().getSimpleName(); // 类型
Annotation[] annoArray = field.getAnnotations(); // 注解
field.setAccessible(true); //获取value要赋予权限
Object obj = clazz.newInstance(); //对象实例
Object value = field.get(obj);// 私有属性需要获取权限才可以
field.set(obj, value + "-----changed..");// 修改私有属性的值
1 /**
2 * 通过反射机制获取类 的属性名及其内容
3 * @param strName
4 * @throws ClassNotFoundException
5 * @throws InstantiationException
6 * @throws IllegalAccessException
7 */
8 public void getClassFieldByName(String strName) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
9 String strClass = getClassName(strName);
10 Class<?> clazz = Class.forName(strClass);
11 Object obj = clazz.newInstance();
12 Field[] fieldArray = clazz.getDeclaredFields(); // 显示所有的属性
13 Field[] publicFieldArray = clazz.getFields(); //显示public属性的元素
14 Field[] newFieldArray = (Field[])ArrayUtils.addAll(fieldArray, publicFieldArray);
15 for(Field field : newFieldArray){
16 String name = field.getName();
17 String modify = Modifier.toString(field.getModifiers());
18 String classType = field.getType().getSimpleName();
19 Annotation[] annoArray = field.getAnnotations();
20 String strAnno = "";
21 for(Annotation anno : annoArray){
22 strAnno += "@"+anno.annotationType().getSimpleName();
23 }
24 field.setAccessible(true);
25 Object value = field.get(obj);// 私有属性需要获取权限才可以
26 System.out.println("propertyName: " + strAnno + " " + modify+ " " + classType + " " + name + "=" + value);
27 if(!StringUtils.contains(modify, "final")){
28 field.set(obj, value + "-----changed..");// 修改私有属性的值
29 System.out.println("propertyName: " + strAnno + " " + modify+ " " + classType + " " + name + "=" + value);
30 }
31 }
32
33 Field[] fieldsArray = clazz.getSuperclass().getDeclaredFields();//父类的属性名
34 for(Field field : fieldsArray){
35 String name = field.getName();
36 String modify = Modifier.toString(field.getModifiers());
37 String classType = field.getType().getSimpleName();
38 field.setAccessible(true);
39 Object value = field.get(obj);// 私有属性需要获取权限才可以
40 System.out.println("superPropertyName: " + modify+ " " + classType + " " + name + "=" + value);
41 }
42 }
getClassFieldByName
>>> reflectFactory.getClassFieldByName("rabit");
运行结果:
propertyName: private String rabitName=I am rabit
propertyName: private String rabitName=I am rabit
propertyName: private String header=
propertyName: private String header=
propertyName: private static final int LEGS=4
propertyName: @Resource public String tails=1tails
propertyName: @Resource public String tails=1tails
propertyName: @Resource public String tails=1tails-----changed..
propertyName: @Resource public String tails=1tails-----changed..
superPropertyName: private static final long serialVersionUID=8482086762730882629
superPropertyName: private int slegs=0
superPropertyName: private int shands=0
superPropertyName: private int sheader=0
4. 获取方法，及方法调用
String modifier = Modifier.toString(method.getModifiers()); //修饰词
String returnType = method.getReturnType().getSimpleName();//返回类型
String name = method.getName();//方法名
Parameter[] parameters = method.getParameters();//参数列表
Annotation[] annoArray = method.getAnnotations();//注解列表
Method method = clazz.getMethod(methodName, classes); //根据方法名，获取方法
method.invoke(obj, orgs)； //方法调用
1 /**
2 * 获取方法并调用方法
3 * @param strName
4 * @param methodName
5 * @param orgs
6 * @param classes
7 * @throws ClassNotFoundException
8 * @throws InstantiationException
9 * @throws IllegalAccessException
10 * @throws NoSuchMethodException
11 * @throws SecurityException
12 * @throws IllegalArgumentException
13 * @throws InvocationTargetException
14 */
15 public void getRunMethodByMethodName(String strName, String methodName, Object[] orgs, Class<?>[] classes) throws ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchMethodException, SecurityException, IllegalArgumentException, InvocationTargetException {
16 String strClass = getClassName(strName);
17 Class<?> clazz = Class.forName(strClass);
18 Class<?> superClazz = clazz.getSuperclass();
19 Object obj = clazz.newInstance();
20 Method[] methodArray = clazz.getDeclaredMethods();
21 Method[] supeMethodArray = superClazz.getDeclaredMethods();
22 Method[] sumMethodArray = (Method[])ArrayUtils.addAll(methodArray, supeMethodArray);
23 for(Method method : sumMethodArray){
24 String modifier = Modifier.toString(method.getModifiers());
25 String returnType = method.getReturnType().getSimpleName();
26 String name = method.getName();
27 Parameter[] parameters = method.getParameters();
28 Annotation[] annoArray = method.getAnnotations();
29 String strAnno = "";
30 for(Annotation anno : annoArray){
31 strAnno += "@"+anno.annotationType().getSimpleName();
32 }
33 String strPara = "";
34 for(Parameter para : parameters){
35 strPara+=para.getType().getSimpleName() + " " + para.getName() + ",";
36 }
37 System.out.println("method:----"+strAnno + " " + modifier + " " + returnType + " " + name + "(" + strPara +")");
38 }
39 Method method = clazz.getMethod(methodName, classes);
40 System.out.println("header: " + method.invoke(obj, orgs));
41 }
getRunMethodByMethodName
>>> Class<?>[] classArray = {String.class,int.class,String.class};
>>> Object[] paramsArray = {"兔子只有",1,"头"};
>>> reflectFactory.getRunMethodByMethodName("rabit", "getHeader",paramsArray, classArray);
运行结果：
method:---- public String getHeader()
method:---- public String getHeader(String arg0,int arg1,String arg2,)
method:---- public int getLegs()
method:---- public int getLegs()
header: 兔子只有[email protected]@@@@@头
5. 构造体方法
clazz.getConstructors() // 获取所有的构造体
----------------------------------------------------------------------------------------------------------
以上，为个人总结，如有写的不当之处，还望指正。
-----------DennyZhao