Java 反射常用方法

JAVA 反射常用的方法

作者:[e-mail]

(1)把List 转化为Map

场景:系统中有一个字典类,是一个实体类,如下(省略了getter,setter方法):

/**
 * Data Dictionary Entity
 */
@Entity
@Table(name = "t_dictionary")
public class CommonDictionary implements Cloneable, Serializable {

    private static final long serialVersionUID = 0x33d260729eadd26eL;

    /**
     * 主键id
     */
    private Long id;
    /**
     * 组id
     */
    private String groupId;
    /**
     * 键<br />不能取值为key,因为key是关键字
     */
    private String key2;
    /**
     * 值
     */
    private String value;
    /**
     * 描述
     */
    private String description;
 public CommonDictionary clone() throws CloneNotSupportedException {
        return (CommonDictionary) super.clone();
    }

 从数据库中查出的结果是List<CommonDictionary> anticounterfeit,我想把它转化为List,CommonDictionary  中的key2作为map的key,CommonDictionary 中的value作为map的value.

方法如下 :

/***
	 * 
	 * @param list
	 * @param clazz
	 * @param keyProperty : 该成员变量的值作为map的key
	 * @param valueProperty : 该成员变量的值作为map的value
	 * @return
	 */
	public static Map<String,Object> parseObjectList(List list,Class clazz,String keyProperty,String valueProperty){
		Map<String,Object> map=new HashMap<String, Object>();
		for(int i=0;i<list.size();i++){
			Object obj=list.get(i);
			Field keyf =null;
			Field valuef =null;
			try {
				keyf = clazz.getDeclaredField(keyProperty);
			} catch (NoSuchFieldException e) {
				keyf= getSpecifiedField(clazz.getSuperclass()/*
															 * may be null if it is
															 * Object .
															 */, keyProperty);
				// e.printStackTrace();
			}
			try {
				valuef = clazz.getDeclaredField(valueProperty);
			} catch (NoSuchFieldException e) {
				valuef= getSpecifiedField(clazz.getSuperclass()/*
															 * may be null if it is
															 * Object .
															 */, valueProperty);
				// e.printStackTrace();
			}
			keyf.setAccessible(true);
			valuef.setAccessible(true);
			try {
				map.put((String)keyf.get(obj), valuef.get(obj));
			} catch (IllegalArgumentException e) {
				e.printStackTrace();
			} catch (IllegalAccessException e) {
				e.printStackTrace();
			}
		}
		return map;
	}

 依赖的方法:

/***
	 * Get Specified Field
	 * 
	 * @param clazz
	 * @param fieldName
	 * @return
	 */
	public static Field getSpecifiedField(Class<?> clazz, String fieldName) {
		Field f = null;
		if (ValueWidget.isNullOrEmpty(clazz)) {
			return null;
		}
		try {
			f = clazz.getDeclaredField(fieldName);
		} catch (NoSuchFieldException e) {
			return getSpecifiedField(clazz.getSuperclass()/*
														 * may be null if it is
														 * Object .
														 */, fieldName);
			// e.printStackTrace();
		}
		return f;
	}

 使用实例:

List<CommonDictionary> anticounterfeit=DictionaryParam.getList(Constant2.DICTIONARY_GROUP_ANTICOUNTERFEIT_CODE);
		QrSettingsBean qrSettingsBean=new QrSettingsBean();
		Map<String,Object>map=ReflectHWUtils.parseObjectList(anticounterfeit, CommonDictionary.class, "key2", "value");
ReflectHWUtils.setObjectValue(qrSettingsBean, map);
		model.addAttribute("qrSettingsBean", qrSettingsBean);

 

 

(2)把Map 转化为java对象,map的key对应对象的成员变量的名称

/***
	 * 利用反射设置对象的属性值. 注意:属性可以没有setter 方法.
	 * 
	 * @param obj
	 * @param params
	 * @throws SecurityException
	 * @throws NoSuchFieldException
	 * @throws IllegalArgumentException
	 * @throws IllegalAccessException
	 */
	public static void setObjectValue(Object obj, Map<String, Object> params)
			throws SecurityException, NoSuchFieldException,
			IllegalArgumentException, IllegalAccessException {
		if (ValueWidget.isNullOrEmpty(params)) {
			return;
		}
		Class<?> clazz = obj.getClass();
		for (Iterator it = params.entrySet().iterator(); it.hasNext();) {
			Map.Entry<String, Object> entry = (Map.Entry<String, Object>) it
					.next();
			String key = entry.getKey();
			Object propertyValue = entry.getValue();
			if (ValueWidget.isNullOrEmpty(propertyValue)) {
				continue;
			}
			Field name = getSpecifiedField(clazz, key);
			if (name != null) {
				name.setAccessible(true);
				name.set(obj, propertyValue);
			}
		}

	}
/***
	 * Get Specified Field
	 * 
	 * @param clazz
	 * @param fieldName
	 * @return
	 */
	public static Field getSpecifiedField(Class<?> clazz, String fieldName) {
		Field f = null;
		if (ValueWidget.isNullOrEmpty(clazz)) {
			return null;
		}
		try {
			f = clazz.getDeclaredField(fieldName);
		} catch (NoSuchFieldException e) {
			return getSpecifiedField(clazz.getSuperclass()/*
														 * may be null if it is
														 * Object .
														 */, fieldName);
			// e.printStackTrace();
		}
		return f;
	}

 

(3)把对象中 值为空字符串的成员变量 ,将其值改为null

/***
	 * 把对象中空字符串改为null
	 * @param obj : 要修改的对象:java bean
	 * @throws SecurityException
	 * @throws NoSuchFieldException
	 * @throws IllegalArgumentException
	 * @throws IllegalAccessException
	 */
	public static void convertEmpty2Null(Object obj) 
			throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException{
		List<Field> fieldsList =getAllFieldList(obj.getClass());
		for(int i=0;i<fieldsList.size();i++){
			Field f=fieldsList.get(i);
			Object vObj=getObjectValue(obj,f );
			if(f.getType().getName().equals("java.lang.String") && (vObj instanceof String) ){
				String str=(String)vObj;
				if(SystemHWUtil.EMPTY.equals(str)){
//					System.out.println(f.getName());
//					System.out.println(f.getType().getName());
					f.setAccessible(true);
					f.set(obj, null);
				}
			}
		}
	}

 依赖的方法:

/***
	 * get all field ,including fields in father/super class
	 * 
	 * @param clazz
	 * @return
	 */
	public static List<Field> getAllFieldList(Class<?> clazz) {
		List<Field> fieldsList = new ArrayList<Field>();// return object
		if (clazz == null) {
			return null;
		}

		Class<?> superClass = clazz.getSuperclass();// father class
		if (!superClass.getName().equals(Object.class.getName()))/*
																 * java.lang.Object
																 */{

			// System.out.println("has father");
			fieldsList.addAll(getAllFieldList(superClass));// Recursive
		}
		Field[] fields = clazz.getDeclaredFields();
		for (int i = 0; i < fields.length; i++) {
			Field field = fields[i];
			// 排除因实现Serializable 接口而产生的属性serialVersionUID
			if (!field.getName().equals("serialVersionUID")) {
				fieldsList.add(field);
			}
		}
		return fieldsList;
	}
/***
	 * 获取指定对象的属性值
	 * 
	 * @param obj
	 * @param name
	 *            :Field
	 * @return
	 * @throws SecurityException
	 * @throws NoSuchFieldException
	 * @throws IllegalArgumentException
	 * @throws IllegalAccessException
	 */
	public static Object getObjectValue(Object obj, Field name)
			throws SecurityException, NoSuchFieldException,
			IllegalArgumentException, IllegalAccessException {

		// Field f = getSpecifiedField(obj.getClass(), name.getName());
		if (name == null) {
			System.out.println("[ReflectHWUtils.getObjectValue]"
					+ obj.getClass().getName() + " does not has field " + name);
			return null;
		}
		name.setAccessible(true);
		return name.get(obj);
	}

 

(4)判断两个对象的属性值是否都相等.

/***
	 * 判断两个对象的属性值是否都相等.
	 * 
	 * @param obj1
	 * @param obj2
	 * @param exclusiveProperties
	 *            : 要过滤的属性
	 * @return
	 * @throws SecurityException
	 * @throws IllegalArgumentException
	 * @throws NoSuchFieldException
	 * @throws IllegalAccessException
	 */
	public static boolean isSamePropertyValue(Object obj1, Object obj2,
			List<String> exclusiveProperties) throws SecurityException,
			IllegalArgumentException, NoSuchFieldException,
			IllegalAccessException {
		List<Field> fieldsList = getAllFieldList(obj1.getClass());
		for (int i = 0; i < fieldsList.size(); i++) {
			Field f = fieldsList.get(i);
			if ((!ValueWidget.isNullOrEmpty(exclusiveProperties))
					&& exclusiveProperties.contains(f.getName())) {// 过滤掉，不比较
				continue;
			}
			Object propertyValue1 = getObjectValue(obj1, f);
			Object propertyValue2 = getObjectValue(obj2, f);

			System.out.println(f.getName());
			if (propertyValue1 == propertyValue2) {// if propertyValue1 is null
				continue;
			}
			if (!isSameBySimpleTypes(propertyValue1, propertyValue2)) {
				return false;
			}
		}
		return true;
	}

/***
	 * 比较java 基本类型的值是否相同.
	 * 
	 * @param obj1
	 *            : String,Integer,Double,Boolean
	 * @param obj2
	 * @return
	 */
	public static boolean isSameBySimpleTypes(Object obj1, Object obj2) {
		if (obj1 == obj2) {
			return true;
		}
		if (obj1 instanceof Integer) {// int
			Integer int1 = (Integer) obj1;
			Integer int2 = (Integer) obj2;
			return int1.intValue() == int2.intValue();
		} else if (obj1 instanceof Double) {// double
			Double double1 = (Double) obj1;
			Double double2 = (Double) obj2;
			return double1.compareTo(double2) == 0;
		} else if (obj1 instanceof Boolean) {// double
			Boolean boolean1 = (Boolean) obj1;
			Boolean boolean2 = (Boolean) obj2;
			return boolean1.compareTo(boolean2) == 0;
		} else if (obj1 instanceof String) {
			String str1 = (String) obj1;
			String str2 = (String) obj2;
			return str1.equals(str2);
		} else if (obj1 instanceof Timestamp) {
			Timestamp time1 = (Timestamp) obj1;
			Timestamp time2 = (Timestamp) obj2;
			return time1.compareTo(time2) == 0;
		} else if (obj1 instanceof java.util.Date) {
			java.util.Date time1 = (java.util.Date) obj1;
			java.util.Date time2 = (java.util.Date) obj2;
			return time1.compareTo(time2) == 0;
		} else if (obj1 instanceof java.sql.Date) {
			java.sql.Date time1 = (java.sql.Date) obj1;
			java.sql.Date time2 = (java.sql.Date) obj2;
			return time1.compareTo(time2) == 0;
		}
		return obj1 == obj2;
	}

/***
	 * 获取指定对象的属性值
	 * 
	 * @param obj
	 * @param name
	 *            :Field
	 * @return
	 * @throws SecurityException
	 * @throws NoSuchFieldException
	 * @throws IllegalArgumentException
	 * @throws IllegalAccessException
	 */
	public static Object getObjectValue(Object obj, Field name)
			throws SecurityException, NoSuchFieldException,
			IllegalArgumentException, IllegalAccessException {

		// Field f = getSpecifiedField(obj.getClass(), name.getName());
		if (name == null) {
			System.out.println("[ReflectHWUtils.getObjectValue]"
					+ obj.getClass().getName() + " does not has field " + name);
			return null;
		}
		name.setAccessible(true);
		return name.get(obj);
	}

 

设置静态成员变量

    /***
     * 动态设置com.chanjet.gov.service.API 静态成员变量的值<br>
     *     注意:应用商店有多台主机进行负载均衡,所以设置完了不一定生效
     * @param key
     * @param val
     * @return
     */
    @RequestMapping(value = "/setAPIprops", produces = Constant.RESPONSE_CONTENTTYPE_PLAIN_UTF)
    @ResponseBody
    public String setAPIproperties(String key,String val) {
        if(!StringUtil.isNullOrEmpty(key)){
            try {
                Field field= API.class.getDeclaredField(key);
                field.setAccessible(true);
                try {
                    field.set(null,val);
                    return val;
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                    return e.getMessage();
                }
            } catch (NoSuchFieldException e) {
                e.printStackTrace();
                return e.getMessage();
            }
        }
        return "failed";
    }

 

作者:[e-mail]

源码见附件