为每个线程创建一个非线程安全对象，并使用“发生前”保证

我想将SAAJ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？
• Jaxp object caching for MessageFactory

这里有一个有趣的小证明，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 据说

尽管 SAAJ 规范没有明确要求线程安全，但 Sun 的引用实现中的 SOAPConnection 似乎是线程安全的。

但我仍然不认为这足以证明SAAJ类是线程安全的。

所以我的问题：下面的成语是正确的吗？我使用主线程内可能的非线程安全工厂创建一个 SOAPConnection 和 MessageFactory 对象，然后使用 CompleteService 接口的 happen-before 保证将这些对象安全地发布到执行器任务。我还使用这种发生之前保证来提取结果HashMap对象。

基本上，我只想验证我推理的合理性。

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;
}