Java 通过反射将所有值从一个类中的字段复制到另一个类中
我有一个类,基本上是另一个类的副本Java 通过反射将所有值从一个类中的字段复制到另一个类中,java,reflection,Java,Reflection,我有一个类,基本上是另一个类的副本 public class A { int a; String b; } public class CopyA { int a; String b; } 我所做的是将classA中的值放入CopyA中,然后通过webservice调用发送CopyA。现在我想创建一个反射方法,它基本上将所有相同的字段(按名称和类型)从classa复制到classCopyA 我该怎么做 到目前为止,这就是我所拥有的,但它不太管用。我想这里的问题是,我试图在我循环
public class A {
int a;
String b;
}
public class CopyA {
int a;
String b;
}
我所做的是将classA
中的值放入CopyA
中,然后通过webservice调用发送CopyA
。现在我想创建一个反射方法,它基本上将所有相同的字段(按名称和类型)从classa
复制到classCopyA
我该怎么做
到目前为止,这就是我所拥有的,但它不太管用。我想这里的问题是,我试图在我循环通过的场上设置一个场
private <T extends Object, Y extends Object> void copyFields(T from, Y too) {
Class<? extends Object> fromClass = from.getClass();
Field[] fromFields = fromClass.getDeclaredFields();
Class<? extends Object> tooClass = too.getClass();
Field[] tooFields = tooClass.getDeclaredFields();
if (fromFields != null && tooFields != null) {
for (Field tooF : tooFields) {
logger.debug("toofield name #0 and type #1", tooF.getName(), tooF.getType().toString());
try {
// Check if that fields exists in the other method
Field fromF = fromClass.getDeclaredField(tooF.getName());
if (fromF.getType().equals(tooF.getType())) {
tooF.set(tooF, fromF);
}
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchFieldException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
private void copyFields(T from,Y也){
班级
2012年11月19日更新:现在也有了一个。如果您不介意使用第三方库,来自Apache Commons的将非常容易地处理这个问题,使用copyProperties(Object,Object)
tof.set()
的第一个参数应该是目标对象(太),而不是字段,第二个参数应该是值,而不是值来自的字段。(要获取值,需要调用fromF.get()
——再次传入目标对象,在本例中是from
)
大多数反射API都是这样工作的。您可以从类而不是实例中获取字段
对象、方法
对象等,以便使用它们(静态除外)您通常需要向它们传递一个实例。BeanUtils只复制公共字段,速度有点慢。请使用getter和setter方法
public Object loadData (RideHotelsService object_a) throws Exception{
Method[] gettersAndSetters = object_a.getClass().getMethods();
for (int i = 0; i < gettersAndSetters.length; i++) {
String methodName = gettersAndSetters[i].getName();
try{
if(methodName.startsWith("get")){
this.getClass().getMethod(methodName.replaceFirst("get", "set") , gettersAndSetters[i].getReturnType() ).invoke(this, gettersAndSetters[i].invoke(object_a, null));
}else if(methodName.startsWith("is") ){
this.getClass().getMethod(methodName.replaceFirst("is", "set") , gettersAndSetters[i].getReturnType() ).invoke(this, gettersAndSetters[i].invoke(object_a, null));
}
}catch (NoSuchMethodException e) {
// TODO: handle exception
}catch (IllegalArgumentException e) {
// TODO: handle exception
}
}
return null;
}
public Object loadData(RideHotelsService Object_a)引发异常{
方法[]gettersAndSetters=object_a.getClass().getMethods();
for(int i=0;i
我想你可以试试。它很好地支持bean到bean的转换。
它也很容易使用,您可以将它注入到spring应用程序中,或者在类路径中添加jar并完成它
有关您案例的示例:
DozerMapper mapper = new DozerMapper();
A a= new A();
CopyA copyA = new CopyA();
a.set... // set fields of a.
mapper.map(a,copyOfA); // will copy all fields from a to copyA
Orika是一个简单而快速的bean映射框架,因为它是通过字节码生成的。它可以进行嵌套映射和不同名称的映射。有关更多详细信息,请
样例映射可能看起来很复杂,但对于复杂场景,它会很简单
MapperFactory factory = new DefaultMapperFactory.Builder().build();
mapperFactory.registerClassMap(mapperFactory.classMap(Book.class,BookDto.class).byDefault().toClassMap());
MapperFacade mapper = factory.getMapperFacade();
BookDto bookDto = mapperFacade.map(book, BookDto.class);
因为这个原因,我不想给另一个JAR文件添加依赖项,所以写了一些适合我需要的东西。我遵循fjorm的惯例,这意味着我通常可以访问的字段是公共的,我不需要费心编写setter和getter(在我看来,代码更容易管理,实际上更可读)
所以我写了一些适合我需要的东西(实际上并不难)(假设这个类有没有参数的公共构造函数),它可以被提取到实用类中
public Effect copyUsingReflection() {
Constructor constructorToUse = null;
for (Constructor constructor : this.getClass().getConstructors()) {
if (constructor.getParameterTypes().length == 0) {
constructorToUse = constructor;
constructorToUse.setAccessible(true);
}
}
if (constructorToUse != null) {
try {
Effect copyOfEffect = (Effect) constructorToUse.newInstance();
for (Field field : this.getClass().getFields()) {
try {
Object valueToCopy = field.get(this);
//if it has field of the same type (Effect in this case), call the method to copy it recursively
if (valueToCopy instanceof Effect) {
valueToCopy = ((Effect) valueToCopy).copyUsingReflection();
}
//TODO add here other special types of fields, like Maps, Lists, etc.
field.set(copyOfEffect, valueToCopy);
} catch (IllegalArgumentException | IllegalAccessException ex) {
Logger.getLogger(Effect.class.getName()).log(Level.SEVERE, null, ex);
}
}
return copyOfEffect;
} catch (InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException ex) {
Logger.getLogger(Effect.class.getName()).log(Level.SEVERE, null, ex);
}
}
return null;
}
不使用BeanUtils或Apache Commons
公共静态无效副本(T1
origEntity,T2 destEntity)抛出非法访问异常,无此字段异常{
Field[]fields=origEntity.getClass().getDeclaredFields();
用于(字段:字段){
集合(destEntity,field.get(origEntity));
}
}
如果依赖项中有spring,也可以使用org.springframework.beans.BeanUtils
我的解决方案:
public static <T > void copyAllFields(T to, T from) {
Class<T> clazz = (Class<T>) from.getClass();
// OR:
// Class<T> clazz = (Class<T>) to.getClass();
List<Field> fields = getAllModelFields(clazz);
if (fields != null) {
for (Field field : fields) {
try {
field.setAccessible(true);
field.set(to,field.get(from));
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}
}
public static List<Field> getAllModelFields(Class aClass) {
List<Field> fields = new ArrayList<>();
do {
Collections.addAll(fields, aClass.getDeclaredFields());
aClass = aClass.getSuperclass();
} while (aClass != null);
return fields;
}
公共静态void copyAllFields(T到,T从){
类clazz=(类)from.getClass();
//或:
//类clazz=(类)到.getClass();
列表字段=getAllModelFields(clazz);
如果(字段!=null){
用于(字段:字段){
试一试{
字段。setAccessible(true);
field.set(to,field.get(from));
}捕获(非法访问例外e){
e、 printStackTrace();
}
}
}
}
公共静态列表getAllModelFields(类aClass){
列表字段=新的ArrayList();
做{
Collections.addAll(fields,aClass.getDeclaredFields());
aClass=aClass.getSuperclass();
}while(aClass!=null);
返回字段;
}
为什么不使用gson库
您只需将类A转换为json字符串。然后将jsonString转换为子类(CopyA)。使用以下代码:
Gson gson= new Gson();
String tmp = gson.toJson(a);
CopyA myObject = gson.fromJson(tmp,CopyA.class);
Spring有一个内置的BeanUtils.copyProperties
方法。但是它不适用于没有getter/setter的类。JSON序列化/反序列化可以是复制字段的另一个选项。Jackson可以用于此目的。如果在大多数情况下使用Spring,Jackson已经在依赖项列表中
ObjectMapper mapper=new ObjectMapper().configure(在未知属性上反序列化feature.FAIL,false);
Clazz copyObject=mapper.readValue(mapper.writeValueAsString(sourceObject),Clazz.class);
这是一个行之有效的解决方案。您可以控制类层次结构中映射的深度
public class FieldMapper {
public static void copy(Object from, Object to) throws Exception {
FieldMapper.copy(from, to, Object.class);
}
public static void copy(Object from, Object to, Class depth) throws Exception {
Class fromClass = from.getClass();
Class toClass = to.getClass();
List<Field> fromFields = collectFields(fromClass, depth);
List<Field> toFields = collectFields(toClass, depth);
Field target;
for (Field source : fromFields) {
if ((target = findAndRemove(source, toFields)) != null) {
target.set(to, source.get(from));
}
}
}
private static List<Field> collectFields(Class c, Class depth) {
List<Field> accessibleFields = new ArrayList<>();
do {
int modifiers;
for (Field field : c.getDeclaredFields()) {
modifiers = field.getModifiers();
if (!Modifier.isStatic(modifiers) && Modifier.isPublic(modifiers)) {
accessibleFields.add(field);
}
}
c = c.getSuperclass();
} while (c != null && c != depth);
return accessibleFields;
}
private static Field findAndRemove(Field field, List<Field> fields) {
Field actual;
for (Iterator<Field> i = fields.iterator(); i.hasNext();) {
actual = i.next();
if (field.getName().equals(actual.getName())
&& field.getType().equals(actual.getType())) {
i.remove();
return actual;
}
}
return null;
}
}
公共类字段映射器{
公共静态无效副本(对象从、对象到)引发异常{
FieldMapper.copy(from、to、Object.class);
}
公共图书馆
public class FieldMapper {
public static void copy(Object from, Object to) throws Exception {
FieldMapper.copy(from, to, Object.class);
}
public static void copy(Object from, Object to, Class depth) throws Exception {
Class fromClass = from.getClass();
Class toClass = to.getClass();
List<Field> fromFields = collectFields(fromClass, depth);
List<Field> toFields = collectFields(toClass, depth);
Field target;
for (Field source : fromFields) {
if ((target = findAndRemove(source, toFields)) != null) {
target.set(to, source.get(from));
}
}
}
private static List<Field> collectFields(Class c, Class depth) {
List<Field> accessibleFields = new ArrayList<>();
do {
int modifiers;
for (Field field : c.getDeclaredFields()) {
modifiers = field.getModifiers();
if (!Modifier.isStatic(modifiers) && Modifier.isPublic(modifiers)) {
accessibleFields.add(field);
}
}
c = c.getSuperclass();
} while (c != null && c != depth);
return accessibleFields;
}
private static Field findAndRemove(Field field, List<Field> fields) {
Field actual;
for (Iterator<Field> i = fields.iterator(); i.hasNext();) {
actual = i.next();
if (field.getName().equals(actual.getName())
&& field.getType().equals(actual.getType())) {
i.remove();
return actual;
}
}
return null;
}
}
object FieldMapper {
fun <T:Any> copy(to: T, from: T) {
try {
val fromClass = from.javaClass
val fromFields = getAllFields(fromClass)
fromFields?.let {
for (field in fromFields) {
try {
field.isAccessible = true
field.set(to, field.get(from))
} catch (e: IllegalAccessException) {
e.printStackTrace()
}
}
}
} catch (e: Exception) {
e.printStackTrace()
}
}
private fun getAllFields(paramClass: Class<*>): List<Field> {
var theClass:Class<*>? = paramClass
val fields = ArrayList<Field>()
try {
while (theClass != null) {
Collections.addAll(fields, *theClass?.declaredFields)
theClass = theClass?.superclass
}
}catch (e:Exception){
e.printStackTrace()
}
return fields
}
static public <X extends Object> X copy(X object, String... skipFields) {
Constructor constructorToUse = null;
for (Constructor constructor : object.getClass().getConstructors()) {
if (constructor.getParameterTypes().length == 0) {
constructorToUse = constructor;
constructorToUse.setAccessible(true);
break;
}
}
if (constructorToUse == null) {
throw new IllegalStateException(object + " must have a zero arg constructor in order to be copied");
}
X copy;
try {
copy = (X) constructorToUse.newInstance();
for (Field field : FieldUtils.getAllFields(object.getClass())) {
if (Modifier.isStatic(field.getModifiers())) {
continue;
}
//Avoid the fields that you don't want to copy. Note, if you pass in "id", it will skip any field with "id" in it. So be careful.
if (StringUtils.containsAny(field.getName(), skipFields)) {
continue;
}
field.setAccessible(true);
Object valueToCopy = field.get(object);
//TODO add here other special types of fields, like Maps, Lists, etc.
field.set(copy, valueToCopy);
}
} catch (InstantiationException | IllegalAccessException | IllegalArgumentException
| InvocationTargetException e) {
throw new IllegalStateException("Could not copy " + object, e);
}
return copy;
}
public <T1 extends Object, T2 extends Object> void copy(T1 origEntity, T2 destEntity) {
DozerBeanMapper mapper = new DozerBeanMapper();
mapper.map(origEntity,destEntity);
}
<dependency>
<groupId>net.sf.dozer</groupId>
<artifactId>dozer</artifactId>
<version>5.4.0</version>
</dependency>
public static <T> void copyAvalableFields(@NotNull T source, @NotNull T target) throws IllegalAccessException {
Field[] fields = source.getClass().getDeclaredFields();
for (Field field : fields) {
if (!Modifier.isStatic(field.getModifiers())
&& !Modifier.isFinal(field.getModifiers())) {
field.set(target, field.get(source));
}
}
}