Java JAX-RS 客户端线程安全吗
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Is JAX-RS Client Thread Safe
提问by wen
In Java EE7, the JAX-RS Client API provides a high-level API for accessing any REST resources. According to the documentation, "Clients are heavy-weight objects that manage the client-side communication infrastructure. Initialization as well as disposal of a Client instance may be a rather expensive operation. It is therefore advised to construct only a small number of Client instances in the application. "
在 Java EE7 中，JAX-RS 客户端 API 提供了用于访问任何 REST 资源的高级 API。根据文档，“客户端是管理客户端通信基础设施的重量级对象。客户端实例的初始化和处置可能是一个相当昂贵的操作。因此建议只构建少量的客户端实例在申请中。”
In order to avoid create client frequently, I am going to cache the client instance and reuse it. Is the client instance thread safe since it can be used by concurrent threads? Is there any performance issue if I only create a instance of the client and reuse it for all the requests?
为了避免频繁创建客户端，我准备缓存客户端实例并重用它。客户端实例线程是否安全，因为它可以被并发线程使用？如果我只创建客户端的一个实例并将其重用于所有请求，是否有任何性能问题？
采纳答案by tddmonkey
The JavaDoc is mostly answering your question already- yes it's thread-safe and you can and should reuse it. There can be a performance issue from notreusing it, i.e. if you create a Client for every HTTP request you make your performance will suck really bad.
JavaDoc 主要已经回答了您的问题 - 是的，它是线程安全的，您可以而且应该重用它。不重用它可能会导致性能问题，即如果您为每个 HTTP 请求创建一个客户端，您的性能将非常糟糕。
回答by Renan
I am not sure but I think this is a implementation-specific decision.
我不确定，但我认为这是一个特定于实现的决定。
I couldn't find in the JAX-RS 2.0 specification nor in the Javadoc anything granting that javax.ws.rs.client.Client is thread-safe. But in the Resteasy (an implementor of JAX-RS) documentation I found:
我在 JAX-RS 2.0 规范和 Javadoc 中都找不到任何允许 javax.ws.rs.client.Client 是线程安全的。但是在 Resteasy（JAX-RS 的实现者）文档中我发现：
One default decision made by HttpClient and adopted by Resteasy is the use of org.apache.http.impl.conn.SingleClientConnManager, which manages a single socket at any given time and which supports the use case in which one or more invocations are made serially from a single thread. For multithreaded applications, SingleClientConnManager may be replaced by org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager:
HttpClient 做出并被 Resteasy 采用的一个默认决定是使用 org.apache.http.impl.conn.SingleClientConnManager，它在任何给定时间管理单个套接字，并支持一个或多个连续调用的用例从一个线程。对于多线程应用，SingleClientConnManager 可能被 org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager 替换：
ClientConnectionManager cm = new ThreadSafeClientConnManager();
HttpClient httpClient = new DefaultHttpClient(cm);
ApacheHttpClient4Engine engine = new ApacheHttpClient4Engine(httpClient);
来源：http: //docs.jboss.org/resteasy/docs/3.0.9.Final/userguide/html/RESTEasy_Client_Framework.html#transport_layer
Based in these information I guess that the answer for your question is likely to be "no".
根据这些信息，我猜您的问题的答案很可能是“否”。
