引用通告地址:
1. 得到某個對象的屬性
1?public?Object getProperty(Object owner, String fieldName)?throws?Exception {
2?????Class ownerClass?=?owner.getClass();
3?
4?????Field field?=?ownerClass.getField(fieldName);
5?
6?????Object property?=?field.get(owner);
7?
8?????return?property;
9?}
2?????Class ownerClass?=?owner.getClass();
3?
4?????Field field?=?ownerClass.getField(fieldName);
5?
6?????Object property?=?field.get(owner);
7?
8?????return?property;
9?}
Class ownerClass = owner.getClass()：得到該對象的Class。
Field field = ownerClass.getField(fieldName)：通過Class得到類聲明的屬性。
Object property = field.get(owner)：通過對象得到該屬性的實例，如果這個屬性是非公有的，這里會報IllegalAccessException。
2. 得到某個類的靜態屬性
?1?public?Object getStaticProperty(String className, String fieldName)
?2?????????????throws?Exception {
?3?????Class ownerClass?=?Class.forName(className);
?4?
?5?????Field field?=?ownerClass.getField(fieldName);
?6?
?7?????Object property?=?field.get(ownerClass);
?8?
?9?????return?property;
10?}
?2?????????????throws?Exception {
?3?????Class ownerClass?=?Class.forName(className);
?4?
?5?????Field field?=?ownerClass.getField(fieldName);
?6?
?7?????Object property?=?field.get(ownerClass);
?8?
?9?????return?property;
10?}
Class ownerClass = Class.forName(className) ：首先得到這個類的Class。
Field field = ownerClass.getField(fieldName)：和上面一樣，通過Class得到類聲明的屬性。
Object property = field.get(ownerClass) ：這里和上面有些不同，因為該屬性是靜態的，所以直接從類的Class里取。
3. 執行某對象的方法
?1?public?Object invokeMethod(Object owner, String methodName, Object[] args)?throws?Exception {
?2?
?3?????Class ownerClass?=?owner.getClass();
?4?
?5?????Class[] argsClass?=?new?Class[args.length];
?6?
?7?????for?(int?i?=?0, j?=?args.length; i?<?j; i++) {
?8?????????argsClass[i]?=?args[i].getClass();
?9?????}
10?
11?????Method method?=?ownerClass.getMethod(methodName, argsClass);
12?
13?????return?method.invoke(owner, args);
14?}
?2?
?3?????Class ownerClass?=?owner.getClass();
?4?
?5?????Class[] argsClass?=?new?Class[args.length];
?6?
?7?????for?(int?i?=?0, j?=?args.length; i?<?j; i++) {
?8?????????argsClass[i]?=?args[i].getClass();
?9?????}
10?
11?????Method method?=?ownerClass.getMethod(methodName, argsClass);
12?
13?????return?method.invoke(owner, args);
14?}
Class owner_class = owner.getClass() ：首先還是必須得到這個對象的Class。
5～9行：配置參數的Class數組，作為尋找Method的條件。
Method method = ownerClass.getMethod(methodName, argsClass)：通過Method名和參數的Class數組得到要執行的Method。
method.invoke(owner, args)：執行該Method，invoke方法的參數是執行這個方法的對象，和參數數組。返回值是Object，也既是該方法的返回值。
4. 執行某個類的靜態方法
?1?public?Object invokeStaticMethod(String className, String methodName,
?2?????????????Object[] args)?throws?Exception {
?3?????Class ownerClass?=?Class.forName(className);
?4?
?5?????Class[] argsClass?=?new?Class[args.length];
?6?
?7?????for?(int?i?=?0, j?=?args.length; i?<?j; i++) {
?8?????????argsClass[i]?=?args[i].getClass();
?9?????}
10?
11?????Method method?=?ownerClass.getMethod(methodName, argsClass);
12?
13?????return?method.invoke(null, args);
14?}
?2?????????????Object[] args)?throws?Exception {
?3?????Class ownerClass?=?Class.forName(className);
?4?
?5?????Class[] argsClass?=?new?Class[args.length];
?6?
?7?????for?(int?i?=?0, j?=?args.length; i?<?j; i++) {
?8?????????argsClass[i]?=?args[i].getClass();
?9?????}
10?
11?????Method method?=?ownerClass.getMethod(methodName, argsClass);
12?
13?????return?method.invoke(null, args);
14?}
基本的原理和實例3相同，不同點是最后一行，invoke的一個參數是null，因為這是靜態方法，不需要借助實例運行。
5. 新建實例
?1?
?2?public?Object newInstance(String className, Object[] args)?throws?Exception {
?3?????Class newoneClass?=?Class.forName(className);
?4?
?5?????Class[] argsClass?=?new?Class[args.length];
?6?
?7?????for?(int?i?=?0, j?=?args.length; i?<?j; i++) {
?8?????????argsClass[i]?=?args[i].getClass();
?9?????}
10?
11?????Constructor cons?=?newoneClass.getConstructor(argsClass);
12?
13?????return?cons.newInstance(args);
14?
15?}
?2?public?Object newInstance(String className, Object[] args)?throws?Exception {
?3?????Class newoneClass?=?Class.forName(className);
?4?
?5?????Class[] argsClass?=?new?Class[args.length];
?6?
?7?????for?(int?i?=?0, j?=?args.length; i?<?j; i++) {
?8?????????argsClass[i]?=?args[i].getClass();
?9?????}
10?
11?????Constructor cons?=?newoneClass.getConstructor(argsClass);
12?
13?????return?cons.newInstance(args);
14?
15?}
這里說的方法是執行帶參數的構造函數來新建實例的方法。如果不需要參數，可以直接使用newoneClass.newInstance()來實現。
Class newoneClass = Class.forName(className)：第一步，得到要構造的實例的Class。
第5～第9行：得到參數的Class數組。
Constructor cons = newoneClass.getConstructor(argsClass)：得到構造子。
cons.newInstance(args)：新建實例。
6. 判斷是否為某個類的實例
1?public?boolean?isInstance(Object obj, Class cls) {
2?????return?cls.isInstance(obj);
3?}
2?????return?cls.isInstance(obj);
3?}
7. 得到數組中的某個元素
1?public?Object getByArray(Object array,?int?index) {
2?????return?Array.get(array,index);
3?}
2?????return?Array.get(array,index);
3?}
附完整源碼：
import?java.lang.reflect.Array;
import?java.lang.reflect.Constructor;
import?java.lang.reflect.Field;
import?java.lang.reflect.Method;
/**
?* Java Reflection Cookbook
?*
?*?@author?Michael Lee
?*?@since?2006-8-23
?*?@version?0.1a
?*/
public?class?Reflection {
????/**
?????* 得到某個對象的公共屬性
?????*
?????*?@param?owner, fieldName
?????*?@return?該屬性對象
?????*?@throws?Exception
?????*
?????*/
????public?Object getProperty(Object owner, String fieldName)?throws?Exception {
????????Class ownerClass?=?owner.getClass();
????????Field field?=?ownerClass.getField(fieldName);
????????Object property?=?field.get(owner);
????????return?property;
????}
????/**
?????* 得到某類的靜態公共屬性
?????*
?????*?@param?className?? 類名
?????*?@param?fieldName?? 屬性名
?????*?@return?該屬性對象
?????*?@throws?Exception
?????*/
????public?Object getStaticProperty(String className, String fieldName)
????????????throws?Exception {
????????Class ownerClass?=?Class.forName(className);
????????Field field?=?ownerClass.getField(fieldName);
????????Object property?=?field.get(ownerClass);
????????return?property;
????}
????/**
?????* 執行某對象方法
?????*
?????*?@param?owner
?????*??????????? 對象
?????*?@param?methodName
?????*??????????? 方法名
?????*?@param?args
?????*??????????? 參數
?????*?@return?方法返回值
?????*?@throws?Exception
?????*/
????public?Object invokeMethod(Object owner, String methodName, Object[] args)
????????????throws?Exception {
????????Class ownerClass?=?owner.getClass();
????????Class[] argsClass?=?new?Class[args.length];
????????for?(int?i?=?0, j?=?args.length; i?<?j; i++) {
????????????argsClass[i]?=?args[i].getClass();
????????}
????????Method method?=?ownerClass.getMethod(methodName, argsClass);
????????return?method.invoke(owner, args);
????}
??????/**
?????* 執行某類的靜態方法
?????*
?????*?@param?className
?????*??????????? 類名
?????*?@param?methodName
?????*??????????? 方法名
?????*?@param?args
?????*??????????? 參數數組
?????*?@return?執行方法返回的結果
?????*?@throws?Exception
?????*/
????public?Object invokeStaticMethod(String className, String methodName,
????????????Object[] args)?throws?Exception {
????????Class ownerClass?=?Class.forName(className);
????????Class[] argsClass?=?new?Class[args.length];
????????for?(int?i?=?0, j?=?args.length; i?<?j; i++) {
????????????argsClass[i]?=?args[i].getClass();
????????}
????????Method method?=?ownerClass.getMethod(methodName, argsClass);
????????return?method.invoke(null, args);
????}
????/**
?????* 新建實例
?????*
?????*?@param?className
?????*??????????? 類名
?????*?@param?args
?????*??????????? 構造函數的參數
?????*?@return?新建的實例
?????*?@throws?Exception
?????*/
????public?Object newInstance(String className, Object[] args)?throws?Exception {
????????Class newoneClass?=?Class.forName(className);
????????Class[] argsClass?=?new?Class[args.length];
????????for?(int?i?=?0, j?=?args.length; i?<?j; i++) {
????????????argsClass[i]?=?args[i].getClass();
????????}
????????Constructor cons?=?newoneClass.getConstructor(argsClass);
????????return?cons.newInstance(args);
????}
????
????/**
?????* 是不是某個類的實例
?????*?@param?obj 實例
?????*?@param?cls 類
?????*?@return?如果 obj 是此類的實例，則返回 true
?????*/
????public?boolean?isInstance(Object obj, Class cls) {
????????return?cls.isInstance(obj);
????}
????
????/**
?????* 得到數組中的某個元素
?????*?@param?array 數組
?????*?@param?index 索引
?????*?@return?返回指定數組對象中索引組件的值
?????*/
????public?Object getByArray(Object array,?int?index) {
????????return?Array.get(array,index);
????}
}
import?java.lang.reflect.Constructor;
import?java.lang.reflect.Field;
import?java.lang.reflect.Method;
/**
?* Java Reflection Cookbook
?*
?*?@author?Michael Lee
?*?@since?2006-8-23
?*?@version?0.1a
?*/
public?class?Reflection {
????/**
?????* 得到某個對象的公共屬性
?????*
?????*?@param?owner, fieldName
?????*?@return?該屬性對象
?????*?@throws?Exception
?????*
?????*/
????public?Object getProperty(Object owner, String fieldName)?throws?Exception {
????????Class ownerClass?=?owner.getClass();
????????Field field?=?ownerClass.getField(fieldName);
????????Object property?=?field.get(owner);
????????return?property;
????}
????/**
?????* 得到某類的靜態公共屬性
?????*
?????*?@param?className?? 類名
?????*?@param?fieldName?? 屬性名
?????*?@return?該屬性對象
?????*?@throws?Exception
?????*/
????public?Object getStaticProperty(String className, String fieldName)
????????????throws?Exception {
????????Class ownerClass?=?Class.forName(className);
????????Field field?=?ownerClass.getField(fieldName);
????????Object property?=?field.get(ownerClass);
????????return?property;
????}
????/**
?????* 執行某對象方法
?????*
?????*?@param?owner
?????*??????????? 對象
?????*?@param?methodName
?????*??????????? 方法名
?????*?@param?args
?????*??????????? 參數
?????*?@return?方法返回值
?????*?@throws?Exception
?????*/
????public?Object invokeMethod(Object owner, String methodName, Object[] args)
????????????throws?Exception {
????????Class ownerClass?=?owner.getClass();
????????Class[] argsClass?=?new?Class[args.length];
????????for?(int?i?=?0, j?=?args.length; i?<?j; i++) {
????????????argsClass[i]?=?args[i].getClass();
????????}
????????Method method?=?ownerClass.getMethod(methodName, argsClass);
????????return?method.invoke(owner, args);
????}
??????/**
?????* 執行某類的靜態方法
?????*
?????*?@param?className
?????*??????????? 類名
?????*?@param?methodName
?????*??????????? 方法名
?????*?@param?args
?????*??????????? 參數數組
?????*?@return?執行方法返回的結果
?????*?@throws?Exception
?????*/
????public?Object invokeStaticMethod(String className, String methodName,
????????????Object[] args)?throws?Exception {
????????Class ownerClass?=?Class.forName(className);
????????Class[] argsClass?=?new?Class[args.length];
????????for?(int?i?=?0, j?=?args.length; i?<?j; i++) {
????????????argsClass[i]?=?args[i].getClass();
????????}
????????Method method?=?ownerClass.getMethod(methodName, argsClass);
????????return?method.invoke(null, args);
????}
????/**
?????* 新建實例
?????*
?????*?@param?className
?????*??????????? 類名
?????*?@param?args
?????*??????????? 構造函數的參數
?????*?@return?新建的實例
?????*?@throws?Exception
?????*/
????public?Object newInstance(String className, Object[] args)?throws?Exception {
????????Class newoneClass?=?Class.forName(className);
????????Class[] argsClass?=?new?Class[args.length];
????????for?(int?i?=?0, j?=?args.length; i?<?j; i++) {
????????????argsClass[i]?=?args[i].getClass();
????????}
????????Constructor cons?=?newoneClass.getConstructor(argsClass);
????????return?cons.newInstance(args);
????}
????
????/**
?????* 是不是某個類的實例
?????*?@param?obj 實例
?????*?@param?cls 類
?????*?@return?如果 obj 是此類的實例，則返回 true
?????*/
????public?boolean?isInstance(Object obj, Class cls) {
????????return?cls.isInstance(obj);
????}
????
????/**
?????* 得到數組中的某個元素
?????*?@param?array 數組
?????*?@param?index 索引
?????*?@return?返回指定數組對象中索引組件的值
?????*/
????public?Object getByArray(Object array,?int?index) {
????????return?Array.get(array,index);
????}
}
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