Java 反射常用方法 博客分类： JavaJava Web 反射reflectlist转化为map获取私有变量的值访问私有变量
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2024-02-24 12:20:06
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JAVA 反射常用的方法
作者:1287789687@qq.com
(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:1287789687@qq.com
源码见附件
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