迷你网络服务器模拟：java.net.SocketException：连接重置

Question

我制作了一个小型“网络服务器”作为 JUnit 测试的模拟。这是“网络服务器”的代码：

while(true) {

    try {
        ServerSocket socket = new ServerSocket(port);
        socket.setReuseAddress(true);
        Socket remote = s.accept();
        PrintWriter out = new PrintWriter(remote.getOutputStream(), true);
        out.append("some data");
        out.flush();
        out.close();    
        remote.close(); 
        socket.close();
    }
    catch (IOException e) { 
        throw new RuntimeException(e);
    }

这就是我在程序代码中所做的事情：

    URL url = new URL(urlstr);  
    HttpURLConnection con = (HttpURLConnection) url.openConnection();
    con.connect();
    MyClass myClass = (MyClass) unmarshaller.unmarshal(con.getInputStream());
    con.disconnect();
    return myClass;

这里是我的问题：有时有效，有时无效。我不知道为什么。我收到此错误：

java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:180)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:230)
at java.io.BufferedInputStream.read1(BufferedInputStream.java:270)
at java.io.BufferedInputStream.read(BufferedInputStream.java:329)
at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:688)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:633)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:653)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1067)
at my.program.Program.myMethod(...)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:48)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:600)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:73)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:46)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:180)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:41)
at org.junit.runners.ParentRunner$1.evaluate(ParentRunner.java:173)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
at org.junit.runners.ParentRunner.run(ParentRunner.java:220)
at org.junit.runners.Suite.runChild(Suite.java:115)
at org.junit.runners.Suite.runChild(Suite.java:23)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:180)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:41)
at org.junit.runners.ParentRunner$1.evaluate(ParentRunner.java:173)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
at org.junit.runners.ParentRunner.run(ParentRunner.java:220)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:46)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

为什么它有时会起作用？为什么有时不呢？怎么了？我必须运行我的 junit 测试 5 到 10 次才能让它工作一次。

Answer 1

间接的答案是：不要尝试自己做。使用嵌入式 Simple 或 Jetty 服务器。使用大致相同数量的代码，您将获得超出您所拥有的相对大量的功能，并且您也不会遇到像这样的奇怪问题。

发生“连接重置”是因为您在 url 连接准备好之前关闭了套接字。

Answer 2

您发布的代码块执行 HTTP 连接和响应的解组。当关注点很好分离时，单元测试效果最好。这意味着为连接和解组逻辑创建单独的类。完成此操作后，您可以使用如下代码测试解组：

class Unmarshaller {
  public MyClass unmarshal(InputStream is) {
    return (MyClass) unmarshaller.unmarsal(is);
  }
}

class UnmarshallerTests {
  @Test
  public void testUnmarshal() {
    Unmarshaller u = new Unmarshaller();
    FileInputStream fis = new FileInputStream("test-sample.xml");
    u.unmarshal(fis);
}

您现在可以使用任何类型的 InputStream 测试解组器。在本例中，我使用了磁盘中的示例 XML 文件。