Java基础巩固系列 通过反射获取类的完整结构——Field（属性篇）

因为演示需要，所以把Person类尽量的造得尽可能的复杂，如下

Person类：

@MyAnnotation(value = "PeterLi")
public class Person extends Creature implements Comparable, MyInterface {
    public String name;
    private int age;
    int id;
    protected boolean sex;

    //创建类时，尽量保留一个空参的构造器
    public Person() {
//        System.out.println("今天天气很闷热");
    }

    public Person(String name) {
        this.name = name;
    }

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @MyAnnotation(value = "abc123")
    public void show() {
        System.out.println("我是一个人！");
    }

    public void display(String nation) throws Exception{
        System.out.println("我的国籍是" + nation);
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    @Override
    public int compareTo(Object o) {
        return 0;
    }

    class Bird{

    }
}

Creature父类：

public class Creature {
    public double weight;

    public void breath() {
        System.out.println("呼吸");
    }

}

 

MyInterface接口：

public interface MyInterface extends Serializable {

}

MyAnnotation注解：

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

 

下面是代码示例：

public class TestField {

    //获取对应的运行时类的属性
    @Test
    public void test1() {
        Class clazz = Person.class;
        //1.getFields:只能获取到运行时类中及其父类中声明为public的属性
        Field[] fields = clazz.getFields();
        for (Field field : fields) {
            System.out.println(field);
        }
        System.out.println();
        //2.getDeclaredFields()：获取运行时类本身声明的所有的属性
        Field[] fields1 = clazz.getDeclaredFields();
        for (Field f : fields1) {
            System.out.println(f);
        }
    }

    //权限修饰符 变量类型 变量名
    //获取属性的各个部分的内容
    @Test
    public void test2() {
        Class clazz = Person.class;
        Field[] fields1 = clazz.getDeclaredFields();
        for (Field f : fields1) {
            //1.获取每个属性的权限修饰符
            int i = f.getModifiers();
            String str1 = Modifier.toString(i);
            System.out.print(i);
            System.out.print(" " + str1 + " ");
            //2.获取属性的变量类型
            Class type = f.getType();
            System.out.print("属性的变量类型：" + type.getName() + " ");

            //3.获取属性名
            System.out.print(f.getName());

            System.out.println();
        }
    }


}

test1结果：

public java.lang.String com.peter.java19.Person.name
public double com.peter.java19.Creature.weight

public java.lang.String com.peter.java19.Person.name
private int com.peter.java19.Person.age
int com.peter.java19.Person.id
protected boolean com.peter.java19.Person.sex

test2结果：

1 public 属性的变量类型：java.lang.String name
2 private 属性的变量类型：int age
0  属性的变量类型：int id
4 protected 属性的变量类型：boolean sex