How to get the property value of an object field using Java reflection?

Java reflection gets the field attribute value

Reflection gets all the fields of the Java class, including all fields in the parent class. The fields of the class itself can be obtained directly through the method

getDeclaredFields() [get all modifier fields] or getFields() [get public modified fields], but there is no direct way to obtain the fields in the parent class. .

Need to recursively obtain all parent classes, then obtain their fields, and finally obtain all fields of the class.

If you want to get the field value, you need to set the field to be accessible: field.setAccessible(true); field is the Field class under the reflect package

Case

1. Parent class

package com.carl.study.springboot.bean; 
import lombok.Data;
import lombok.experimental.Accessors;
 
/**
 * @author changez
 * @desc
 * @date 2019/3/10 11:30
 */
@Data
@Accessors(chain = true)
public class BeanBasic {
 
    private Integer id;
    private Long createTime;
    private Long updateTime;
}

2. Subclass

package com.carl.study.springboot.bean; 
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.ToString;
import lombok.experimental.Accessors;
 
/**
 * @author changez
 * @desc
 * @date 2019/3/10 11:17
 */
@Data
@EqualsAndHashCode(callSuper = true)
@ToString(callSuper = true)
@Accessors(chain = true)
public class Student extends BeanBasic{
 
    private String name;
    private String address;
}

3. Test class, get all fields of student class

package test.lombok; 
import com.carl.study.springboot.bean.Student;
import org.junit.Test; 
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
 
/**
 * @author changez
 * @desc Java反射获取类的所有属性.
 * @date 2019/3/10 11:41
 */
public class LombokTest {
 
    @Test
    public void getParentField(){
        Student stu1 = new Student();
        stu1.setName("student-name")
            .setAddress("student1-address")
            .setId(1)
            .setCreateTime(20190310140423L)
            .setUpdateTime(20190310140423L)
        ;
 
        Class clazz = Student.class;
        List<Field> allFields = new ArrayList<>(100);
 
        // 获取当前对象的所有属性字段
        // clazz.getFields()：获取public修饰的字段
        // clazz.getDeclaredFields()： 获取所有的字段包括private修饰的字段
        allFields.addAll(Arrays.asList(clazz.getDeclaredFields()));
 
        // 获取所有父类的字段， 父类中的字段需要逐级获取
        Class clazzSuper = clazz.getSuperclass();
 
        // 如果父类不是object，表明其继承的有其他类。 逐级获取所有父类的字段
        while (clazzSuper != Object.class) {
            allFields.addAll(Arrays.asList(clazzSuper.getDeclaredFields()));
            clazzSuper = clazzSuper.getSuperclass();
        }
 
        allFields.stream().forEach(field -> {
 
            // 设置字段可访问， 否则无法访问private修饰的变量值
            field.setAccessible(true);
            try {
                // 获取字段名称
                String fieldName = field.getName();
 
                // 获取指定对象的当前字段的值
                Object fieldVal = field.get(stu1);
                System.out.println(fieldName+"="+fieldVal);
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        });
    }
}

4. Result output

The reflection object obtains the properties and values ​​​​into string

Description

Sometimes it is necessary to splice the passing objects in the form of kv. In this case, it is good to use reflection

Directly enter the code

public class FanSeVo {
    private String name;
    private String id;
    //.......
    // 如果是跟外部程序或者接口对接的话，下面还可以加2个属性，一个是相互约定的秘钥，一个//是排除秘钥之后对属性和值做凭借之后的MD5加密之后的值，可以做数据安全考虑，防止传输过程数据被篡改
}

package com.ycj.my_all_demo.fanse;
import java.lang.reflect.Field;
import java.util.HashMap;
/**
 * @author ycj
 * @data 17:55
 */
public class FanSe {
    public static void main(String[] args) {
        FanSeVo fanSeVo = new FanSeVo("1", "2");
        Field[] fields = fanSeVo.getClass().getDeclaredFields();
        HashMap<String, String> map = new HashMap<>();
        for (Field field : fields) {
            field.setAccessible(true);
            try {
            // 把对象的属性做k，值做v
            // 当然中间还可做其他的业务操作，比如跳过某些属性什么的
                String name = field.getName();
                String s = field.get(fanSeVo).toString();
                map.put(name,s);
                System.out.println();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        // 吧map数据转成str，kv的形式
        String strByMap = getStrByMap(map);
        System.out.println(strByMap);//name1id2
    }
    public static String getStrByMap(HashMap<String, String> map){
        StringBuilder str = new StringBuilder();
        map.forEach((k,v)->{str.append(k).append(v);});
        return str.toString();
    }
}

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