java SE – reflect

測試類別

package testReflect;/**  * @Package testReflect * @ClassName: Hello * @Description: TODO() * @author andy * @date 2013-5-31 上午09:59:29 */public class Hello {    public String name;    private int id = 1;        public Hello(){            }    public Hello(String name,int id){        this.name = name;        this.id = id;    }            public String getUserName(){        return "123";    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }}

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獲得某個類或對象的運行時Class的對象的三種方式

package testReflect;/**  * @Package testReflect * @ClassName: InstancingClass * @Description: TODO(獲得某個類或對象的運行時Class的對象的三種方式) * @author andy * @date 2013-5-31 上午09:59:05 */public class InstancingClass<T> {    public static void main(String[] args) throws ClassNotFoundException {        //第一種        Class<Hello> classType1 = Hello.class;        //第二種        Class<?> classType2 = Class.forName("testReflect.Hello");        //第三種        Hello hello = new Hello();        Class<? extends Hello> classType3 = hello.getClass();                System.out.println(classType1 + "\n" +classType2 + "\n" + classType3 + "\n");        System.out.println(classType1.getName() + "\n" +classType2.getName() + "\n" + classType3.getName() + "\n");        System.out.println(classType1.getSimpleName() + "\n" +classType2.getSimpleName() + "\n" + classType3.getSimpleName() + "\n");    }}

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不用new關鍵字執行個體化對象的三種方法

package testReflect;import java.lang.reflect.Constructor;import java.lang.reflect.InvocationTargetException;/**  * @Package testReflect * @ClassName: InstancingObject * @Description: TODO(不用new關鍵字執行個體化對象的三種方法) * @author andy * @date 2013-5-31 上午10:08:34 */public class InstancingObject {    public static void main(String[] args) throws InstantiationException, IllegalAccessException, NoSuchMethodException, SecurityException, IllegalArgumentException, InvocationTargetException {        Hello hello0 = Hello.class.newInstance();                Class<Hello> classType = Hello.class;                //建構函式沒有參數時，第一種等價於第二種        //第一種        Hello hello1 = (Hello) classType.newInstance();                //第二種        Constructor<Hello> con = classType.getConstructor();        Hello hello2 = (Hello) con.newInstance();                //第三種        Constructor<Hello> con2 = classType.getConstructor(new Class[]{String.class, int.class});        Hello hello3 =  (Hello)con2.newInstance(new Object[]{"123",123});                System.out.println(hello0.getUserName());        System.out.println(hello1.getUserName());        System.out.println(hello2.getUserName());        System.out.println(hello3.getUserName());    }}

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通過反射對欄位的操作

package testReflect;import java.lang.reflect.AccessibleObject;import java.lang.reflect.Field;/**  * @Package testReflect * @ClassName: AccessFieldByReflect * @Description: TODO(通過反射對欄位的操作) * @author andy * @date 2013-5-31 上午10:48:13 */public class AccessFieldByReflect {    public static void main(String[] args) throws IllegalArgumentException, IllegalAccessException, InstantiationException {        Hello hello = Hello.class.newInstance();        Field[] fields = hello.getClass().getDeclaredFields();        //遍曆擷取所有的欄位        for(Field field : fields){            //System.out.println(field);            System.out.println(field.getName());        }        System.out.println("沒有修改前：" + hello.getName());        System.out.println("沒有修改前：" + hello.getId());        for(Field field : fields){            if("id".equals(field.getName())){                //允許訪問所有Field、Method 和 Constructor 私人元素                field.setAccessible(true);                //指定只允許訪問的Field                AccessibleObject[] accessParam = {field};                Field.setAccessible(accessParam,true);                //如果那個欄位是int就setint,是double就setdouble                field.setInt(hello, 123);            }else{                //欄位是字串                field.set(hello, "張三");            }        }                System.out.println("通過反射修改後：" + hello.getId());        System.out.println("通過反射修改後：" + hello.getName());    }}

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通過反射對方法的操作

package testReflect;import java.lang.reflect.AccessibleObject;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;/**  * @Package testReflect * @ClassName: AccessMethodByReflect * @Description: TODO(通過反射對方法的操作) * @author andy * @date 2013-5-31 上午11:25:39 */public class AccessMethodByReflect {    public static void main(String[] args) throws IllegalArgumentException, IllegalAccessException, InstantiationException, InvocationTargetException, NoSuchMethodException, SecurityException {        Hello hello = Hello.class.newInstance();        Method[] methods = hello.getClass().getDeclaredMethods();        //遍曆擷取所有的欄位        for(Method method : methods){            //System.out.println(field);            System.out.println(method.getName());        }        System.out.println("沒有修改前：" + hello.getName());        System.out.println("沒有修改前：" + hello.getId());        for(Method method : methods){            if("setId".equals(method.getName())){                //允許訪問所有Field、Method 和 Constructor 私人元素                method.setAccessible(true);                //只允許訪問指定的Method                AccessibleObject[] accessParam = {method};                Method.setAccessible(accessParam,true);            }else if("setName".equals(method.getName())){                method.invoke(hello, "張三");            }        }                String obj = (String) hello.getClass().getDeclaredMethod("getName").invoke(hello);         System.out.println("通過反射getName方法返回來的值：" + obj);        System.out.println("通過反射修改後：" + hello.getId());        System.out.println("通過反射修改後：" + hello.getName());            }}

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Integer.TYPE 返回的int，即返回的是它們所對應的原生資料class對象(所有的封裝類都是這樣的),

Integer.class 返回的是它所對應的Class對象 java.lang.Integer