[Web Service] Rop在进行响应或输入的序列化时存在线程安全问题

最新推荐文章于 2021-05-21 21:09:16 发布

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最新推荐文章于 2021-05-21 21:09:16 发布

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stamen 2012-05-17

    由于我原来的Marshaller是一个RopResponse对应一个实例，也即一个RopResponse类是共享一个单实例的Marshaller。当时，我认为Marshaller是线程安全的，但是经过测试，Marshaller是非线程安全的：
    可以看这篇文章：
http://jaxb.java.net/guide/Performance_and_thread_safety.html
    我马上会修复这个BUG的。

引用收藏

stamen 2012-05-18

RopResponseMarshaller的实现类包括以下两个：

JacksonJsonRopResponseMarshaller：内部使用org.codehaus.jackson.map.ObjectMapper进行JSON序列化
JaxbXmlRopResponseMarshaller：内部使用javax.xml.bind.Marshaller进行XML序列化

org.codehaus.jackson.map.ObjectMapper是线程安全的(参见： http://wiki.fasterxml.com/JacksonFAQThreadSafety)，而javax.xml.bind.Marshaller是非线程安全的。原来的Rop对ObjectMapper和Marshaller都采用了单实例的方式，因此存在线程安全的问题。

关于javax.xml.bind.Marshaller非线程安全的说明参见： http://jaxb.java.net/guide/Performance_and_thread_safety.html

不但javax.xml.bind.Marshaller是非线程安全的，Spring OXM的Marshaller也是非线程安全的，参见其javadoc的说明：

引用

createMarshaller

protected Marshaller createMarshaller()
Return a newly created JAXB marshaller. JAXB marshallers are not necessarily thread safe.

原来的JaxbXmlRopResponseMarshaller：

Java代码

public class JaxbXmlRopResponseMarshaller implements RopResponseMarshaller {
private static Map<Class, Marshaller> marshallerMap = new HashMap<Class, Marshaller>();
public void marshaller(RopResponse response, OutputStream outputStream) {
try {
Marshaller m = getMarshaller(response);
m.marshal(response, outputStream);
} catch (JAXBException e) {
throw new RopException(e);
}
}
private Marshaller getMarshaller(RopResponse response) throws JAXBException {
if (!marshallerMap.containsKey(response.getClass())) {
JAXBContext context = JAXBContext.newInstance(response.getClass());
Marshaller marshaller = context.createMarshaller();//Marshaller是非线程安全的，不能多线程共用！！！！
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.setProperty(Marshaller.);
marshaller.setProperty(Marshaller.JAXB_ENCODING, "utf-8");
marshallerMap.put(response.getClass(), marshaller);
}
return marshallerMap.get(response.getClass());
}
}

更改为：

Java代码

public class JaxbXmlRopResponseMarshaller implements RopResponseMarshaller {
private static Map<Class, JAXBContext> jaxbContextHashMap = new ConcurrentHashMap<Class, JAXBContext>();
public void marshaller(RopResponse response, OutputStream outputStream) {
try {
Marshaller m = buildMarshaller(response);
m.marshal(response, outputStream);
} catch (JAXBException e) {
throw new RopException(e);
}
}
public Marshaller buildMarshaller(RopResponse response) throws JAXBException {
if (!jaxbContextHashMap.containsKey(response.getClass())) {
JAXBContext context = JAXBContext.newInstance(response.getClass());//JAXBContext是线程安全的
jaxbContextHashMap.put(response.getClass(), context);
}
JAXBContext context = jaxbContextHashMap.get(response.getClass());
Marshaller marshaller = context.createMarshaller();//每次创建一个新的Marshaller
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.setProperty(Marshaller.JAXB_ENCODING, "utf-8");
return marshaller;
}
}