大家好,又见面了,我是你们的朋友全栈君。
BeanUtils
是Apache Commons
组件的成员之一,主要用于简化JavaBean
封装数据的操作。
简化反射封装参数的步骤,给对象封装参数,好处是BeanUtils
给对象封装参数的时候会进行类型自动转换。
public
修饰getter
和setter
方法访问属性<dependency>
<groupId>commons-beanutils</groupId>
<artifactId>commons-beanutils</artifactId>
<version>1.9.4</version>
</dependency>
private static void setUserProperty() throws Exception {
Worker worker = new Worker();
BeanUtils.setProperty(worker, "id", "1");
BeanUtils.setProperty(worker, "name", "哪吒");
BeanUtils.setProperty(worker, "age", "28");
System.out.println("id:"+ BeanUtils.getProperty(worker, "id"));
System.out.println(worker);
}
private static void cloneBean() throws Exception {
Worker worker1 = new Worker(3,"哪吒",18);
// 拷贝对象
Object object = BeanUtils.cloneBean(worker1);
Worker worker2 = (Worker)object;
System.out.println(worker2);//Worker{id=3, name='哪吒', age=18}
System.out.println("worker1==worker2 : "+(worker1==worker2));//false
// 拷贝对象属性
Worker worker3 = new Worker();
BeanUtils.copyProperties(worker3,worker1);
System.out.println(worker3);//Worker{id=3, name='哪吒', age=18}
System.out.println("worker1==worker3 : "+(worker1==worker3));//false
// 为属性赋值
Worker worker4 = new Worker();
BeanUtils.copyProperty(worker4,"age",30);
System.out.println(worker4);//Worker{id=0, name='null', age=30}
}
private static void mapToBean() throws Exception {
Map<String, Object> map = new HashMap<String, Object>();
map.put("id",2);
map.put("name","哪吒");
map.put("age",29);
Worker user = new Worker();
BeanUtils.populate(user,map);
System.out.println(user);
}
private static void beanToMap() throws Exception {
Worker worker = new Worker(4,"哪吒编程",18);
Map<String, String> map = BeanUtils.describe(worker);
System.out.println(map);//{name=哪吒, id=4, age=18}
// 为什么返回值是一个数组呢?
String[] names = BeanUtils.getArrayProperty(worker, "name");
System.out.println(names[0]);
}
默认情况下,使用org.apache.commons.beanutils.BeanUtils
对复杂对象是进行的浅拷贝,但是由于Apache
下的BeanUtils
对象拷贝性能太差,不建议使用,这在阿里巴巴Java开发规约插件上也明确指出:
Ali-Check | 避免用Apache Beanutils进行属性的copy。
到这里你可能会疑惑,为什么会出现拷贝性能差的情况呢?
因为在对对象进行拷贝的时候添加很多的校验,比如像类型转换,甚至还校验了对象所属类的访问权限,可以说校验是相当的复杂,这也就是造成性能差的根本原因,我们看下它的具体代码实现:
public void copyProperties(final Object dest, final Object orig)
throws IllegalAccessException, InvocationTargetException {
// Validate existence of the specified beans
if (dest == null) {
throw new IllegalArgumentException
("No destination bean specified");
}
if (orig == null) {
throw new IllegalArgumentException("No origin bean specified");
}
if (log.isDebugEnabled()) {
log.debug("BeanUtils.copyProperties(" + dest + ", " +
orig + ")");
}
// Copy the properties, converting as necessary
if (orig instanceof DynaBean) {
final DynaProperty[] origDescriptors =
((DynaBean) orig).getDynaClass().getDynaProperties();
for (DynaProperty origDescriptor : origDescriptors) {
final String name = origDescriptor.getName();
// Need to check isReadable() for WrapDynaBean
// (see Jira issue# BEANUTILS-61)
if (getPropertyUtils().isReadable(orig, name) &&
getPropertyUtils().isWriteable(dest, name)) {
final Object value = ((DynaBean) orig).get(name);
copyProperty(dest, name, value);
}
}
} else if (orig instanceof Map) {
@SuppressWarnings("unchecked")
final
// Map properties are always of type <String, Object>
Map<String, Object> propMap = (Map<String, Object>) orig;
for (final Map.Entry<String, Object> entry : propMap.entrySet()) {
final String name = entry.getKey();
if (getPropertyUtils().isWriteable(dest, name)) {
copyProperty(dest, name, entry.getValue());
}
}
} else /* if (orig is a standard JavaBean) */ {
final PropertyDescriptor[] origDescriptors =
getPropertyUtils().getPropertyDescriptors(orig);
for (PropertyDescriptor origDescriptor : origDescriptors) {
final String name = origDescriptor.getName();
if ("class".equals(name)) {
continue; // No point in trying to set an object's class
}
if (getPropertyUtils().isReadable(orig, name) &&
getPropertyUtils().isWriteable(dest, name)) {
try {
final Object value =
getPropertyUtils().getSimpleProperty(orig, name);
copyProperty(dest, name, value);
} catch (final NoSuchMethodException e) {
// Should not happen
}
}
}
}
}
而org.springframework.beans.BeanUtils
是使用 copyProperties
方法进行拷贝,不过实现的方式相对于前者要来得简单得多了,可以说是非常的简单,就是根据两个对象属性的名字进行匹配,做简单的 get/set
,仅检查属性的可访问性。具体实现如下:
private static void copyProperties(Object source, Object target, @Nullable Class<?> editable,
@Nullable String... ignoreProperties) throws BeansException {
Assert.notNull(source, "Source must not be null");
Assert.notNull(target, "Target must not be null");
Class<?> actualEditable = target.getClass();
if (editable != null) {
if (!editable.isInstance(target)) {
throw new IllegalArgumentException("Target class [" + target.getClass().getName() +
"] not assignable to Editable class [" + editable.getName() + "]");
}
actualEditable = editable;
}
PropertyDescriptor[] targetPds = getPropertyDescriptors(actualEditable);
List<String> ignoreList = (ignoreProperties != null ? Arrays.asList(ignoreProperties) : null);
for (PropertyDescriptor targetPd : targetPds) {
Method writeMethod = targetPd.getWriteMethod();
if (writeMethod != null && (ignoreList == null || !ignoreList.contains(targetPd.getName()))) {
PropertyDescriptor sourcePd = getPropertyDescriptor(source.getClass(), targetPd.getName());
if (sourcePd != null) {
Method readMethod = sourcePd.getReadMethod();
if (readMethod != null &&
ClassUtils.isAssignable(writeMethod.getParameterTypes()[0], readMethod.getReturnType())) {
try {
if (!Modifier.isPublic(readMethod.getDeclaringClass().getModifiers())) {
readMethod.setAccessible(true);
}
Object value = readMethod.invoke(source);
if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {
writeMethod.setAccessible(true);
}
writeMethod.invoke(target, value);
}
catch (Throwable ex) {
throw new FatalBeanException(
"Could not copy property '" + targetPd.getName() + "' from source to target", ex);
}
}
}
}
}
}
从上面的实现源码可以看到:成员变量赋值是基于目标对象的成员列表,并且会跳过ignore
以及在源对象中不存在的属性,所以这个方法是安全的,不会因为两个对象之间的结构差异导致错误,但是必须保证同名的两个成员变量类型相同。
以上简要的分析两种BeanUtils
的具体实现以及性能相关的分析,得出结论:Apache下的BeanUtils由于各种繁琐的校验以及可访问性的校验等等,导致性能较差,故实际开发中不建议使用,可以使用 Spring的BeanUtils。
package com.guor.beanutil.spring;
import com.guor.beanutil.Worker;
import org.junit.Test;
import org.springframework.beans.BeanUtils;
public class SpringBeanUtilsTest {
@Test
public void testInstantiate() throws Exception{
//通过无参数构造函数实例化
Object obj = BeanUtils.instantiateClass(Worker.class);
if(obj instanceof Worker) {
System.out.println(((Worker) obj).getNezha());//哪吒
}
//通过有参数构造函数实例化
Object obj2 = BeanUtils.instantiateClass(Worker.class.getDeclaredConstructor(String.class), "哪吒编程");
if(obj2 instanceof Worker) {
System.out.println(((Worker) obj2).getNezha());//哪吒编程
}
}
}
(1)无参调用
@Test
public void testFindDeclaredMethod() throws Exception {
Worker worker = new Worker();
worker.setId(8);
worker.setName("哪吒");
Method method = BeanUtils.findDeclaredMethod(Worker.class, "getName");
Object name = method.invoke(worker);
System.out.println(name);//哪吒
}
(2)有参调用
@Test
public void testPropertyDescriptor2() throws Exception {
Worker worker = new Worker();
worker.setId(10);
worker.setName("哪吒");
Method method = BeanUtils.findMethod(Worker.class, "sayMsg",String.class,String.class);
method.invoke(worker,"哪吒","我很帅");//哪吒 say :我很帅
}
(3)如果找不到方法
@Test
public void testPropertyDescriptor() throws Exception {
Worker worker = new Worker();
worker.setId(10);
worker.setName("哪吒");
//获取属性
PropertyDescriptor pd = BeanUtils.getPropertyDescriptor(Worker.class, "name");
//获取属性的get方法
Method getMethod = pd.getReadMethod();
Object name = getMethod.invoke(worker);
System.out.println(name);//哪吒
//获取属性的get方法
Method setMethod = pd.getWriteMethod();
setMethod.invoke(worker, "哪吒编程");
System.out.println(worker.getName());//哪吒编程
}
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