我想将 SAAJ 中的 SOAPConnectionFactory 和 MessageFactory 类与多个线程一起使用，但事实证明我不能假设它们是线程安全的。
一些相关帖子：
- javax.xml.soap.MessageFactory的实例是线程安全的吗？ https://stackoverflow.com/questions/25279280/javax-xml-soap-messagefactorys-instance-is-thread-safe
- MessageFactory 的 jaxp 对象缓存 https://stackoverflow.com/questions/4203071/jaxp-object-caching-for-messagefactory
这是一个有趣的小证明，证明它可以是线程安全的：http://svn.apache.org/repos/asf/axis/axis2/java/core/tags/v1.5.6/modules/saaj/src/org/apache/axis2/saaj/SOAPConnectionImpl.java http://svn.apache.org/repos/asf/axis/axis2/java/core/tags/v1.5.6/modules/saaj/src/org/apache/axis2/saaj/SOAPConnectionImpl.java据说
尽管 SAAJ 规范没有明确要求线程安全，但 Sun 参考实现中的 SOAPConnection 似乎是线程安全的。
但我仍然认为这不足以证明 SAAJ 类是线程安全的。
所以我的问题是：下面的习语正确吗？我使用主线程内可能非线程安全的工厂创建了一个 SOAPConnection 和 MessageFactory 对象，然后使用 CompletionService 接口的happens-before保证将这些对象安全地发布到执行程序任务。我还使用此发生之前保证来提取结果 HashMap 对象。
基本上我只是想验证我的推理是否合理。
public static void main(String args[]) throws Exception {
ExecutorService executorService = Executors.newFixedThreadPool(10);
CompletionService<Map<String, String>> completionService = new ExecutorCompletionService<>(executorService);
//submitting 100 tasks
for (int i = 0; i < 100; i++) {
// there is no docs on if these classes are thread-safe or not, so creating them before submitting to the
// external thread. This seems to be safe, because we are relying on the happens-before guarantees of the
// CompletionService.
SOAPConnectionFactory soapConnectionFactory = SOAPConnectionFactory.newInstance();
SOAPConnection soapConnection = soapConnectionFactory.createConnection();
MessageFactory messageFactory = MessageFactory.newInstance();
int number = i;// we can't just use i, because it's not effectively final within the task below
completionService.submit(() -> {
// using messageFactory here!
SOAPMessage request = createSOAPRequest(messageFactory, number);
// using soapConnection here!
SOAPMessage soapResponse = soapConnection.call(request, "example.com");
soapConnection.close();
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
soapResponse.writeTo(outputStream);
// HashMap is not thread-safe on its own, but we'll use the happens-before guarantee. See f.get() below.
Map<String, String> result = new HashMap<>();
result.put("soapResponse", new String(outputStream.toByteArray()));
return result;
});
}
// printing the responses as they arrive
for (int i = 0; i < 100; i++) {
Future<Map<String, String>> f = completionService.take();
Map<String, String> result = f.get();
System.out.println(result.get("soapResponse"));
}
executorService.shutdown();
}
/**
* Thread-safe static method
*/
private static SOAPMessage createSOAPRequest(MessageFactory messageFactory, int number) throws Exception {
SOAPMessage soapMessage = messageFactory.createMessage();
SOAPPart soapPart = soapMessage.getSOAPPart();
String serverURI = "example.com";
SOAPEnvelope envelope = soapPart.getEnvelope();
envelope.addNamespaceDeclaration("example", serverURI);
SOAPBody soapBody = envelope.getBody();
SOAPElement soapBodyElem = soapBody.addChildElement("number", "example");
soapBodyElem.addTextNode(String.valueOf(number));
soapMessage.saveChanges();
return soapMessage;
}
