java面试宝典_java面试宝典2016版pdf_java面试题大全带答案(37)

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.List;

/**
 * 反射工具类
 * @author 骆昊
 *
 */
public class ReflectionUtil {

    private ReflectionUtil() {
        throw new AssertionError();
    }

    /**
     * 通过反射取对象指定字段(属性)的值
     * @param target 目标对象
     * @param fieldName 字段的名字
     * @throws 如果取不到对象指定字段的值则抛出异常
     * @return 字段的值
     */
    public static Object getValue(Object target, String fieldName) {
        Class<?> clazz = target.getClass();
        String[] fs = fieldName.split("\\.");

        try {
            for(int i = 0; i < fs.length - 1; i++) {
                Field f = clazz.getDeclaredField(fs[i]);
                f.setAccessible(true);
                target = f.get(target);
                clazz = target.getClass();
            }

            Field f = clazz.getDeclaredField(fs[fs.length - 1]);
            f.setAccessible(true);
            return f.get(target);
        }
        catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * 通过反射给对象的指定字段赋值
     * @param target 目标对象
     * @param fieldName 字段的名称
     * @param value 值
     */
    public static void setValue(Object target, String fieldName, Object value) {
        Class<?> clazz = target.getClass();
        String[] fs = fieldName.split("\\.");
        try {
            for(int i = 0; i < fs.length - 1; i++) {
                Field f = clazz.getDeclaredField(fs[i]);
                f.setAccessible(true);
                Object val = f.get(target);
                if(val == null) {
                    Constructor<?> c = f.getType().getDeclaredConstructor();
                    c.setAccessible(true);
                    val = c.newInstance();
                    f.set(target, val);
                }
                target = val;
                clazz = target.getClass();
            }

            Field f = clazz.getDeclaredField(fs[fs.length - 1]);
            f.setAccessible(true);
            f.set(target, value);
        }
        catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

}

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