java 反射机制详解及实例代码

java 反射机制：

测试实体类

以Human为例

public class Human {
  private String name;
  private int age;
  private float height;

  private static int legs = 2;
  private Map jobs;
  private T t;

  public int say() {
    System.out.println("I'm" + name);
    return 0;
  }
  private void sleep(Human human) {
    System.out.println(name + " sleep with " + human.name);
  }
  public List getList() {
    return new ArrayList<>();
  }
  public Human() {
  }
  private Human(String name, int age, float height) {
    this.name = name;
    this.age = age;
    this.height = height;
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public int getAge() {
    return age;
  }
  public void setAge(int age) {
    if (age > 150 || age < 0) {
      throw new RuntimeException("age > 150 || age < 0");
    }
    this.age = age;
  }
  public float getHeight() {
    return height;
  }
  public void setHeight(float height) {
    this.height = height;
  }
  @Override
  public String toString() {
    return "Human{" +
 "name='" + name + ''' +
 ", age=" + age +
 ", height=" + height +
 '}';
  }
}

测试获取构造方法

public class TestConstructor {
  public static void main(String[] args) {
    //得到相应的类结构, 这是用来描述Human这个类的类
    Class humanClass = Human.class;
    try {
////      这是在知道构造方法结构的前提下
//      //获取都明确参数的构造方法, 获取的是公开的(public)
//      Constructor constructor1 = humanClass.getConstructor(String.class, Integer.TYPE, Float.TYPE);
//
//      Human h1 = constructor1.newInstance("小明", 18, 1.85f);
//      System.out.println(h1.toString());
//
//      //构造方法, 修饰符类型
//      int modifiers = constructor1.getModifiers();
//      if (Modifier.isPublic(modifiers)) {
// System.out.println("是public");
//      }

//      ////获取都明确参数的构造方法, 获取的是声明的
//      Constructor constructor2 = humanClass.getDeclaredConstructor(String.class, Integer.TYPE, Float.TYPE);
//      //设置可以全部访问
//      constructor2.setAccessible(true);
//      //这样是可以获取到所有的构造方法, 包括私有的
//      Human human2 = constructor2.newInstance("zll", 18, 1.80f);
//      System.out.println(human2.toString());

      //不知道构造方法的类结构
      Constructor[] constructors = humanClass.getDeclaredConstructors();

      for (Constructor c : constructors) {
 c.setAccessible(true);
 System.out.println(c.getName());
 System.out.println("===========================");
 //参数列表
 Class[] types = c.getParameterTypes();
 for (Class type : types) {
   System.out.println(type.getTypeName());
 }

 //修饰符类型
 int modifiers = c.getModifiers();
 if (Modifier.isPublic(modifiers)) {
   System.out.println("是公开的");
 }else if (Modifier.isPrivate(modifiers)){
   System.out.println("是私有的");
 }
      }


    } catch (Exception e) {
      e.printStackTrace();
    }

  }
}

测试获取字段

public class TestField {
  public static void main(String[] args) {
    Class humanClass = Human.class;
    Field[] fields = humanClass.getDeclaredFields();
    for (Field f : fields) {

      //属性名
      System.out.print(" 名字: " + f.getName() + " ");
      System.out.println();
      //类型
      System.out.print("类型 :" + f.getType() + " ");
      System.out.println();
      //修饰符
      int modifiers = f.getModifiers();
      if (Modifier.isPublic(modifiers)) {
 System.out.println("公开的");
      } else if (Modifier.isPrivate(modifiers)) {
 System.out.println("私有的");
      }
    }
    System.out.println("============================泛型==================================");
    try {
      //通过类结构获取jobs属性
      Field jobs = humanClass.getDeclaredField("jobs");
      //泛型
      ParameterizedType type = (ParameterizedType) jobs.getAnnotatedType().getType();
      Type[] types = type.getActualTypeArguments();
    for (Type type1 : types) {
 System.out.println(type1);
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
    System.out.println("===================设置值, 得到值============================");

    try {
      Human