杂七杂八

获取类属性

获取类属性有两种方式

• getFields()：获得某个类的所有的公共（public）的字段，包括父类中的字段。
• getDeclaredFields()：获得某个类的所有声明（public、private、proteced）的字段，但是不包括父类的申明字段。

public class TestFields {
    @Test
    public void testFields() {
        Person person = new BoyStudent();
        Arrays.stream(person.getClass().getFields()).forEach(field -> System.out.println("testFields:"+field.getName()));
        Arrays.stream(person.getClass().getDeclaredFields()).forEach(field -> System.out.println("testDeclaredFields:"+field.getName()));
    }

    class Person {
        public String Id;
        private String username;
        private String grade;
    }

    class Student extends Person {
        private String sex;
    }

    class BoyStudent extends Student {
        private String color;
    }
}

测试结果：

testFields:Id
testDeclaredFields:color
testDeclaredFields:this$0

获取全部属性

通过getDeclaredFields()方法获取当前类的所有属性(私有属性、保护属性和公共属性)。然后，递归父类的属性。

public class TestDeclaredFields {

    @Test
    public void test() {
        Field[] fields = getAllFields(new BoyStudent());
        Arrays.stream(fields)
                .distinct()
                .filter(f -> f.getName().equals("username"))
                .findFirst()
                .ifPresent(field -> System.out.println("final:"+field.getName()));
    }

    public Field[] getAllFields(Object object) {
        Class<?> clazz = object.getClass();
        List<Field> fieldList = new ArrayList<>();
        while (clazz != null) {
            fieldList.addAll(Arrays.asList(clazz.getDeclaredFields()));
            clazz = clazz.getSuperclass();
        }
        Field[] fields = new Field[fieldList.size()];
        Arrays.stream(fieldList.toArray(fields)).forEach(f-> System.out.println("fields: "+f.getName()));
        return fields;
    }

    class Person {
        private String username;
        private String grade;
    }

    class Student extends Person {
        private String sex;
    }

    class BoyStudent extends Student {
        private String color;
    }
}

测试结果：

fields: color
fields: this$0
fields: sex
fields: this$0
fields: Id
fields: username
fields: grade
fields: this$0
final:username