Java 反射设置/获取对象属性值

浅浅的花香味﹌ 2024-04-23 16:00 9阅读 0赞

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#### 文章目录 ####

*   *  设置/获取属性
     *   *  方式一
         *  方式二
         *  方式三
     *  场景案例

本文总结：Java 通过反射设置对象属性值，或者获取对象属性值，编码过程中反射结合泛型使用可以代码复用，减少冗余代码；  
食用建议：配合场景案例食用更佳；

### 设置/获取属性 ###

实体类对象：

@AllArgsConstructor
    @NoArgsConstructor
    @Data
    public class StudentScore {
        
        /**
         * 名称
         */
        private String name;
        /**
         * 科目
         */
        private String subject;
        /**
         * 成绩
         */
        private Integer score;
    }

#### 方式一 ####

通过Field操作属性：

public void method1() throws Exception {
        
            Class<StudentScore> cls = StudentScore.class;
            StudentScore obj = new StudentScore();
            StudentScore obj2 = new StudentScore();
            /*
             * 设置属性
             */
            Field nameField = cls.getDeclaredField("name");
            nameField.setAccessible(true);
            nameField.set(obj, "张三");
    
            Field subjectField = cls.getDeclaredField("subject");
            subjectField.setAccessible(true);
            subjectField.set(obj, "语文");
    
            Field scoreField = cls.getDeclaredField("score");
            scoreField.setAccessible(true);
            scoreField.set(obj, 100);
    
            /*
             * 获取属性
             */
            Field[] fields = cls.getDeclaredFields();
            for (Field field : fields) {
        
                String s = Modifier.toString(field.getModifiers());
                // 排除final修饰的属性
                if (!s.contains("final")) {
        
                    field.setAccessible(true);
                    // 通过filed获取设置属性
                    System.out.printf("获取属性值，当前属性：%s，值：%s%n", field.getName(), field.get(obj));
                    // obj对象属性值赋值给obj2
                    field.set(obj2, field.get(obj));
                }
            }
            System.out.println("method1 obj：" + JSONObject.toJSONString(obj));
            System.out.println("method1 obj2：" + JSONObject.toJSONString(obj2));
        }

运行结果：  
![在这里插入图片描述][dd69073aeb5244ccaf6f5f9562dd5c01.png_pic_center]

#### 方式二 ####

通过set方法：

public void method2() throws Exception {
        
            Class<StudentScore> cls = StudentScore.class;
            StudentScore obj = new StudentScore();
    
            /*
             * 设置属性
             */
            Method setName = cls.getMethod("setName", String.class);
            setName.invoke(obj, "李四");
    
            Method setSubject = cls.getMethod("setSubject", String.class);
            setSubject.invoke(obj, "语文");
    
            Method setScore = cls.getMethod("setScore", Integer.class);
            setScore.invoke(obj, 114);
    
            /*
             * 获取属性
             */
            Method getName = cls.getMethod("getName");
            System.out.printf("获取属性值，当前属性：%s，值：%s%n", "name", getName.invoke(obj));
            Method getSubject = cls.getMethod("getSubject");
            System.out.printf("获取属性值，当前属性：%s，值：%s%n", "subject", getSubject.invoke(obj));
            Method getScore = cls.getMethod("getScore");
            System.out.printf("获取属性值，当前属性：%s，值：%s%n", "score", getScore.invoke(obj));
            System.out.println("method2：" + JSONObject.toJSONString(obj));
        }

运行结果：

![在这里插入图片描述][d88f4979773c43e5bcd63a4a4c8d8e26.png_pic_center]

#### 方式三 ####

通过属性名：

public void method3() throws Exception {
        
            Class<StudentScore> cls = StudentScore.class;
            StudentScore obj = new StudentScore();
            /*
             * 设置属性
             */
            PropertyDescriptor namePd = new PropertyDescriptor("name", cls);
            Method writeMethod = namePd.getWriteMethod();
            writeMethod.invoke(obj, "王五");
    
            PropertyDescriptor subjectPd = new PropertyDescriptor("subject", cls);
            Method subjectMethod = subjectPd.getWriteMethod();
            subjectMethod.invoke(obj, "语文");
    
            PropertyDescriptor scorePd = new PropertyDescriptor("score", cls);
            Method scoreMethod = scorePd.getWriteMethod();
            scoreMethod.invoke(obj, 127);
    
            /*
             * 获取属性
             */
            Method nameRead = namePd.getReadMethod();
            System.out.printf("获取属性值，当前属性：%s，值：%s%n", "name", nameRead.invoke(obj));
            Method subjectRead = subjectPd.getReadMethod();
            System.out.printf("获取属性值，当前属性：%s，值：%s%n", "subject", subjectRead.invoke(obj));
            Method scoreRead = scorePd.getReadMethod();
            System.out.printf("获取属性值，当前属性：%s，值：%s%n", "score", scoreRead.invoke(obj));
            System.out.println("method3：" + JSONObject.toJSONString(obj));
        }

运行结果：

![在这里插入图片描述][66396a8c16854de6bf0a1e6e413401dd.png_pic_center]

### 场景案例 ###

场景：学生查询自己的语文考试成绩；

![在这里插入图片描述][f876dfb63c6047d7b35f51ce87e2ae46.png_pic_center]

学生成绩对象实体类:

/**
     * 学生成绩实体
     */
    @AllArgsConstructor
    @NoArgsConstructor
    @Data
    public class StudentScore {
        
    
        /**
         * 名称
         */
        private String name;
        /**
         * 科目
         */
        private String subject;
        /**
         * 成绩
         */
        private Integer score;
    
    }

学生对象实体类：

/**
     * 学生-张三
     */
    @Data
    public class StudentZS extends StudentScore {
        
    }
    /**
     * 学生-李四
     *
     */
    @Data
    public class StudentLS extends StudentScore {
        
    }
    /**
     * 学生-王五
     */
    @Data
    public class StudentWW extends StudentScore {
        
    }

测试：

@Test
    public void testDemo() {
        
        StudentZS student1 = new StudentZS();
        student1.setName("张三");
        scoreSystem(student1, StudentZS.class);
        System.out.println("张三查询成绩结果：" + JSONObject.toJSONString(student1));
    
        StudentLS student2 = new StudentLS();
        student2.setName("李四");
        scoreSystem(student2, StudentLS.class);
        System.out.println("李四查询成绩结果：" + JSONObject.toJSONString(student2));
    
        StudentWW student3 = new StudentWW();
        student3.setName("王五");
        scoreSystem(student3, StudentWW.class);
        System.out.println("王五查询成绩结果：" + JSONObject.toJSONString(student3));
    }
    
    /**
      * 成绩系统
      *
      * @param t   学生
      * @param cls 学生类
      * @param <T> 泛型
      */
    public <T> void scoreSystem(T t, Class<T> cls) {
        
        // 给传入对象赋值名称
        try {
        
            Class<? super T> superclass = cls.getSuperclass();
            Field nameField = superclass.getDeclaredField("name");
            Type genericType = nameField.getGenericType();
            String typeName = genericType.getTypeName();
            assert "java.lang.String".equals(typeName);
            nameField.setAccessible(true);
            String studentName = nameField.get(t).toString();
            int schoolReport = 0;
            switch (studentName) {
        
                case "张三":
                    schoolReport = 100;
                    break;
                case "李四":
                    schoolReport = 114;
                    break;
                case "王五":
                    schoolReport = 127;
                    break;
            }
            Field subjectField = superclass.getDeclaredField("subject");
            subjectField.setAccessible(true);
            subjectField.set(t, "语文");
            Field scoreField = superclass.getDeclaredField("score");
            scoreField.setAccessible(true);
            scoreField.set(t, schoolReport);
        } catch (Exception e) {
        
            e.printStackTrace();
        }
    }

运行结果：  
![在这里插入图片描述][8d2742b9ffda4006bd57beb5255f6f93.png_pic_center]

[dd69073aeb5244ccaf6f5f9562dd5c01.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/23/dd0ae7eaddc84a5484a2b6ed6c5ef353.png
[d88f4979773c43e5bcd63a4a4c8d8e26.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/23/c12b98a4b70d4f119e872f183dffede0.png
[66396a8c16854de6bf0a1e6e413401dd.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/23/536524b399dd4366887f092207892b2e.png
[f876dfb63c6047d7b35f51ce87e2ae46.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/23/8979a32f9ac84d13b1fb5e7a8643ebb4.png
[8d2742b9ffda4006bd57beb5255f6f93.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/23/df3c700bfbaa4f28ad0c1ebb079785dc.png