java-反射2

1.javabean對(duì)象

@MyAnnotation(value="hi")
public class Person extends Creature<String> implements Comparable<String>,MyInterface{
    private String name;
    int age;
    public int id;

    public Person(){}
    @MyAnnotation(value="abc")
    private Person(String name){
        this.name = name;
    }
     Person(String name,int age){
        this.name = name;
        this.age = age;
    }
    @MyAnnotation
    private String show(String nation){
        System.out.println("我的國(guó)籍是：" + nation);
        return nation;
    }
    public String display(String interests,int age) throws NullPointerException,ClassCastException{
        return interests + age;
    }
    @Override
    public void info() {
        System.out.println("我是一個(gè)人");
    }
    @Override
    public int compareTo(String o) {
        return 0;
    }
    private static void showDesc(){
        System.out.println("我是一個(gè)可愛(ài)的人");
    }
    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", id=" + id +
                '}';
    }
}

2.自定義注解

@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
    String value() default "hello";

}

3.接口

public interface MyInterface {
    void info();
}

4.父類

public class Creature<T> implements Serializable {
    private char gender;
    public double weight;

    private void breath(){
        System.out.println("生物呼吸");
    }

    public void eat(){
        System.out.println("生物吃東西");
    }

}

5.開(kāi)始測(cè)試

/**
 * 調(diào)用運(yùn)行時(shí)類中指定的結(jié)構(gòu)：屬性、方法、構(gòu)造器
 *
 */
public class ReflectionTest {

    /*
        不需要掌握
     */
    @Test
    public void testField() throws Exception {
        Class clazz = Person.class;

        //創(chuàng)建運(yùn)行時(shí)類的對(duì)象
        Person p = (Person) clazz.newInstance();

        //獲取指定的屬性：要求運(yùn)行時(shí)類中屬性聲明為public
        //通常不采用此方法
        Field id = clazz.getField("id");

        /*
        設(shè)置當(dāng)前屬性的值

        set():參數(shù)1：指明設(shè)置哪個(gè)對(duì)象的屬性   參數(shù)2：將此屬性值設(shè)置為多少
         */

        id.set(p,1001);

        /*
        獲取當(dāng)前屬性的值
        get():參數(shù)1：獲取哪個(gè)對(duì)象的當(dāng)前屬性值
         */
        int pId = (int) id.get(p);
        System.out.println(pId);


    }
    /*
    如何操作運(yùn)行時(shí)類中的指定的屬性 -- 需要掌握
     */
    @Test
    public void testField1() throws Exception {
        Class clazz = Person.class;

        //創(chuàng)建運(yùn)行時(shí)類的對(duì)象
        Person p = (Person) clazz.newInstance();

        //1. getDeclaredField(String fieldName):獲取運(yùn)行時(shí)類中指定變量名的屬性
        Field name = clazz.getDeclaredField("name");

        //2.保證當(dāng)前屬性是可訪問(wèn)的
        name.setAccessible(true);
        //3.獲取、設(shè)置指定對(duì)象的此屬性值
        name.set(p,"Tom");

        System.out.println(name.get(p));
    }

    /*
    如何操作運(yùn)行時(shí)類中的指定的方法 -- 需要掌握
     */
    @Test
    public void testMethod() throws Exception {

        Class clazz = Person.class;

        //創(chuàng)建運(yùn)行時(shí)類的對(duì)象
        Person p = (Person) clazz.newInstance();

        /*
        1.獲取指定的某個(gè)方法
        getDeclaredMethod():參數(shù)1 ：指明獲取的方法的名稱  參數(shù)2：指明獲取的方法的形參列表
         */
        Method show = clazz.getDeclaredMethod("show", String.class);
        //2.保證當(dāng)前方法是可訪問(wèn)的
        show.setAccessible(true);

        /*
        3. 調(diào)用方法的invoke():參數(shù)1：方法的調(diào)用者  參數(shù)2：給方法形參賦值的實(shí)參
        invoke()的返回值即為對(duì)應(yīng)類中調(diào)用的方法的返回值。
         */
        Object returnValue = show.invoke(p,"CHN"); //String nation = p.show("CHN");
        System.out.println(returnValue);

        System.out.println("*************如何調(diào)用靜態(tài)方法*****************");

        // private static void showDesc()

        Method showDesc = clazz.getDeclaredMethod("showDesc");
        showDesc.setAccessible(true);
        //如果調(diào)用的運(yùn)行時(shí)類中的方法沒(méi)有返回值，則此invoke()返回null
//        Object returnVal = showDesc.invoke(null);
        Object returnVal = showDesc.invoke(Person.class);
        System.out.println(returnVal);//null

    }

    /*
    如何調(diào)用運(yùn)行時(shí)類中的指定的構(gòu)造器
     */
    @Test
    public void testConstructor() throws Exception {
        Class clazz = Person.class;

        //private Person(String name)
        /*
        1.獲取指定的構(gòu)造器
        getDeclaredConstructor():參數(shù)：指明構(gòu)造器的參數(shù)列表
         */

        Constructor constructor = clazz.getDeclaredConstructor(String.class);

        //2.保證此構(gòu)造器是可訪問(wèn)的
        constructor.setAccessible(true);

        //3.調(diào)用此構(gòu)造器創(chuàng)建運(yùn)行時(shí)類的對(duì)象
        Person per = (Person) constructor.newInstance("Tom");
        System.out.println(per);

    }

}

6.測(cè)試Filed

public class FieldTest {

    @Test
    public void test1(){

        Class clazz = Person.class;

        //獲取屬性結(jié)構(gòu)
        //getFields():獲取當(dāng)前運(yùn)行時(shí)類及其父類中聲明為public訪問(wèn)權(quán)限的屬性
        Field[] fields = clazz.getFields();
        for(Field f : fields){
            System.out.println(f);
        }
        System.out.println();

        //getDeclaredFields():獲取當(dāng)前運(yùn)行時(shí)類中聲明的所有屬性。（不包含父類中聲明的屬性）
        Field[] declaredFields = clazz.getDeclaredFields();
        for(Field f : declaredFields){
            System.out.println(f);
        }
    }

    //權(quán)限修飾符  數(shù)據(jù)類型 變量名
    @Test
    public void test2(){
        Class clazz = Person.class;
        Field[] declaredFields = clazz.getDeclaredFields();
        for(Field f : declaredFields){
            //1.權(quán)限修飾符
            int modifier = f.getModifiers();
            System.out.print(Modifier.toString(modifier) + "\t");

            //2.數(shù)據(jù)類型
            Class type = f.getType();
            System.out.print(type.getName() + "\t");

            //3.變量名
            String fName = f.getName();
            System.out.print(fName);

            System.out.println();
        }

    }

}

7.測(cè)試Method

public class MethodTest {

    @Test
    public void test1(){

        Class clazz = Person.class;

        //getMethods():獲取當(dāng)前運(yùn)行時(shí)類及其所有父類中聲明為public權(quán)限的方法
        Method[] methods = clazz.getMethods();
        for(Method m : methods){
            System.out.println(m);
        }
        System.out.println();
        //getDeclaredMethods():獲取當(dāng)前運(yùn)行時(shí)類中聲明的所有方法。（不包含父類中聲明的方法）
        Method[] declaredMethods = clazz.getDeclaredMethods();
        for(Method m : declaredMethods){
            System.out.println(m);
        }
    }

    /*
    @Xxxx
    權(quán)限修飾符  返回值類型  方法名(參數(shù)類型1 形參名1,...) throws XxxException{}
     */
    @Test
    public void test2(){
        Class clazz = Person.class;
        Method[] declaredMethods = clazz.getDeclaredMethods();
        for(Method m : declaredMethods){
            //1.獲取方法聲明的注解
            Annotation[] annos = m.getAnnotations();
            for(Annotation a : annos){
                System.out.println(a);
            }
            //2.權(quán)限修飾符
            System.out.print(Modifier.toString(m.getModifiers()) + "\t");

            //3.返回值類型
            System.out.print(m.getReturnType().getName() + "\t");

            //4.方法名
            System.out.print(m.getName());
            System.out.print("(");
            //5.形參列表
            Class[] parameterTypes = m.getParameterTypes();
            if(!(parameterTypes == null && parameterTypes.length == 0)){
                for(int i = 0;i < parameterTypes.length;i++){

                    if(i == parameterTypes.length - 1){
                        System.out.print(parameterTypes[i].getName() + " args_" + i);
                        break;
                    }

                    System.out.print(parameterTypes[i].getName() + " args_" + i + ",");
                }
            }
            System.out.print(")");

            //6.拋出的異常
            Class[] exceptionTypes = m.getExceptionTypes();
            if(exceptionTypes.length > 0){
                System.out.print("throws ");
                for(int i = 0;i < exceptionTypes.length;i++){
                    if(i == exceptionTypes.length - 1){
                        System.out.print(exceptionTypes[i].getName());
                        break;
                    }

                    System.out.print(exceptionTypes[i].getName() + ",");
                }
            }
            System.out.println();
        }

    }
}

8.測(cè)試其他

public class OtherTest {

    /*
    獲取構(gòu)造器結(jié)構(gòu)

     */
    @Test
    public void test1(){

        Class clazz = Person.class;
        //getConstructors():獲取當(dāng)前運(yùn)行時(shí)類中聲明為public的構(gòu)造器
        Constructor[] constructors = clazz.getConstructors();
        for(Constructor c : constructors){
            System.out.println(c);
        }

        System.out.println();
        //getDeclaredConstructors():獲取當(dāng)前運(yùn)行時(shí)類中聲明的所有的構(gòu)造器
        Constructor[] declaredConstructors = clazz.getDeclaredConstructors();
        for(Constructor c : declaredConstructors){
            System.out.println(c);
        }

    }

    /*
    獲取運(yùn)行時(shí)類的父類

     */
    @Test
    public void test2(){
        Class clazz = Person.class;

        Class superclass = clazz.getSuperclass();
        System.out.println(superclass);
    }

    /*
    獲取運(yùn)行時(shí)類的帶泛型的父類

     */
    @Test
    public void test3(){
        Class clazz = Person.class;

        Type genericSuperclass = clazz.getGenericSuperclass();
        System.out.println(genericSuperclass);
    }

    /*
    獲取運(yùn)行時(shí)類的帶泛型的父類的泛型


    代碼：邏輯性代碼  vs 功能性代碼
     */
    @Test
    public void test4(){
        Class clazz = Person.class;

        Type genericSuperclass = clazz.getGenericSuperclass();
        ParameterizedType paramType = (ParameterizedType) genericSuperclass;
        //獲取泛型類型
        Type[] actualTypeArguments = paramType.getActualTypeArguments();
//        System.out.println(actualTypeArguments[0].getTypeName());
        System.out.println(((Class)actualTypeArguments[0]).getName());
    }

    /*
    獲取運(yùn)行時(shí)類實(shí)現(xiàn)的接口
     */
    @Test
    public void test5(){
        Class clazz = Person.class;

        Class[] interfaces = clazz.getInterfaces();
        for(Class c : interfaces){
            System.out.println(c);
        }

        System.out.println();
        //獲取運(yùn)行時(shí)類的父類實(shí)現(xiàn)的接口
        Class[] interfaces1 = clazz.getSuperclass().getInterfaces();
        for(Class c : interfaces1){
            System.out.println(c);
        }

    }
    /*
        獲取運(yùn)行時(shí)類所在的包

     */
    @Test
    public void test6(){
        Class clazz = Person.class;

        Package pack = clazz.getPackage();
        System.out.println(pack);
    }

    /*
        獲取運(yùn)行時(shí)類聲明的注解

     */
    @Test
    public void test7(){
        Class clazz = Person.class;

        Annotation[] annotations = clazz.getAnnotations();
        for(Annotation annos : annotations){
            System.out.println(annos);
        }
    }

}

posted on 2022-08-30 16:17 從精通到陌生閱讀(33) 評(píng)論(0) 收藏舉報(bào)