Java反射工具類

1.反射工具類，代碼如下

package com.pmo.util;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.math.BigDecimal;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.List;

/**
 * Created by ASUS on 2019/9/9.
 * 反射工具類
 */
public class ReflectTool {

    private ReflectTool(){};

    /**
     * 獲取字段對應值，並轉為String類型，空值返回空字符串
     * @param fieldName
     * @param obj
     * @return
     */
    public static synchronized String getStringValue(String fieldName,Object obj) throws  ReflectiveOperationException{
        Object objectValue = getValueByGetter(fieldName,obj);
        if (objectValue == null){
            return "";
        }
        String result = objectValue.toString();
        //如果類型為BigDecimal,去掉末尾的0
        if (objectValue instanceof BigDecimal){
            BigDecimal value = (BigDecimal) objectValue;
            value = value.stripTrailingZeros();
            result = value.toPlainString();
        }else if (objectValue instanceof Date){
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            result = sdf.format((Date)objectValue).replace(" 00:00:00", "");
        }

        return result.trim();
    }

    public static Object getValueByGetter (String fieldName,Object obj) throws ReflectiveOperationException {
        Method getter = getGetter(fieldName, obj.getClass());
        if (getter != null){
            return getter.invoke(obj);
        }

        return null;
    }


    public static Object setValueBySetter (String fieldName,Object obj) throws ReflectiveOperationException {
        Method setter = getSetter(fieldName, obj.getClass());
        if (setter == null){
            throw new ReflectiveOperationException("沒有set方法");
    }

        return setter.invoke(obj);
    }

    /**
     * 獲取get方法
     * @param fieldName
     * @param cls
     * @return
     */
    public static Method getGetter(String fieldName,Class<?> cls){
        for (Method method : cls.getMethods()) {
            if (method.getName().equalsIgnoreCase("get".concat(fieldName)) && method.getParameterTypes().length == 0){
                return  method;
            }
        }
        return null;
    }

    /**
     * 獲取set方法
     * @param fieldName
     * @param cls
     * @return
     */
    public static Method getSetter(String fieldName,Class<?> cls){
        for (Method method : cls.getMethods()) {
            if (method.getName().equalsIgnoreCase("set".concat(fieldName)) && method.getParameterTypes().length == 0){
                return  method;
            }
        }
        return null;
    }

    /**
     * 通過屬性名獲取Field對象
     * @param fieldName
     * @param cls
     * @return
     */
    public static synchronized Field getFieldByName(String fieldName,Class<?> cls){
        Field[] fields =cls.getDeclaredFields();
        for (Field field : fields){
            if (field.getName().equals(fieldName)){
                return field;
            }
        }

        if (cls.getSuperclass() != null){
            return getFieldByName(fieldName,cls.getSuperclass());
        }

        return null;
    }

    /**
     * 通過對象.class獲取所有Fields，包括父類
     * @param cls
     * @return
     */
    public static List<Field> listFields(Class<?> cls){
        Field[] fs = cls.getDeclaredFields();
        List<Field> fields = new ArrayList<>(Arrays.asList(fs));
        if (cls.getSuperclass() !=null){
            fields.addAll(listFields(cls.getSuperclass()));
        }
        return fields;
    }

    public static  boolean fieldExist(String fieldName,Class<?> cls){
        return getFieldByName(fieldName, cls) !=null;
    }
}

2.寫一個Persion類，和一個Students類測試

Persion代碼如下：

package com.pmo.vo;

/**
 * Created by ASUS on 2019/9/9.
 */
public class Persion {

    private  String name;

    private int age;

    public int getAge() {
        return age;
    }

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

    public String getName() {
        return name;
    }

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

Students類代碼如下：

package com.pmo.vo;

/**
 * Created by ASUS on 2019/9/9.
 */
public class Students extends  Persion {

    private int score;//總分數

    public int getScore() {
        return score;
    }

    public void setScore(int score) {
        this.score = score;
    }
}

package com.pmo.vo;

/**
 * Created by ASUS on 2019/9/9.
 */
public class Students extends  Persion {

    private int score;//總分數

    public int getScore() {
        return score;
    }

    public void setScore(int score) {
        this.score = score;
    }
}

3.寫一個Test測試

package com.pmo.vo;

import com.pmo.util.ReflectTool;

import java.lang.reflect.Field;
import java.util.List;

/**
 * Created by ASUS on 2019/9/9.
 */
public class Test {

          public static void main(String[] args) throws ReflectiveOperationException {
              Students students = new Students();

              students.setName("張三");
              students.setAge(100);
              students.setScore(700);

              Field field  = ReflectTool.getFieldByName("name", students.getClass());
              System.out.println("反射獲取Field對象：" + field);

              String name1 = ReflectTool.getStringValue("name", students);
              System.out.println("反射獲取name值：" + name1);

              List<Field> fields = ReflectTool.listFields(students.getClass());
              System.out.println("反射獲取所有filed,包括父類"+fields.toString());


          }

}

效果如下：

反射獲取Field對象：private java.lang.String com.pmo.vo.Persion.name
反射獲取name值：張三
反射獲取所有filed,包括父類[private int com.pmo.vo.Students.score, private java.lang.String com.pmo.vo.Persion.name, private int com.pmo.vo.Persion.age]