我尝试在服务器上使用Java Serlvet在Webapp中实现Server-Sent-Event。Java Servlet和SSE中的连接关闭
是否可以在Servlet中检查连接是否被客户端关闭?即使客户端浏览器关闭,Servlet中的循环while(true)
也是无限的。
客户端代码
function startLogSSE(lastEventId, level) {
var eventSource = new EventSource("log-sse?last-event-id=" + lastEventId + "&level=" + level);
eventSource.onmessage = function (event) {
document.getElementById('log').innerHTML = event.data + "\n" + document.getElementById('log').innerHTML;
};
}
Server代码
public class LogSSEServlet extends HttpServlet {
private static final Logger logger = LoggerFactory.getLogger(LogSSEServlet.class);
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/event-stream");
response.setCharacterEncoding("UTF-8");
PrintWriter writer = response.getWriter();
// get logger purgerDB appender
PurgerDBAppender appender = LogUtils.getPurgerDBAppender();
if (appender == null) {
writer.write("data: [ERROR] Appender 'purgerDB' isn't found for logger 'com.bp3'\n\n");
writer.close();
return;
}
int eventId = 0;
// get last-event-id
String lastEventId = request.getHeader("last-event-id");
if (lastEventId == null) {
// try to get lastEventId from parameter
lastEventId = request.getParameter("last-event-id");
}
if (lastEventId != null) {
try {
eventId = Integer.parseInt(lastEventId);
} catch (NumberFormatException e) {
logger.error("Failed to parse last-event-id: " + lastEventId);
}
}
String minLevel = request.getParameter("level");
if (minLevel == null) {
minLevel = "TRACE";
}
// get logs from purgerDB logger appender
LogServices logServices = new LogServices();
try {
logServices.open();
} catch (SQLException e) {
throw new ServletException(e);
}
try {
while (true) {
List<LogMessage> messages = logServices.getLastMessages(Level.toLevel(minLevel), eventId, 0);
if (messages.size() > 0) {
writer.write("id: " + messages.get(0).getEventId() + "\n");
writer.write("data: " + LogUtils.formatLog(messages) + "\n");
writer.flush();
}
try {
Thread.sleep(100);
} catch (InterruptedException e) {
break;
}
}
} catch (SQLException e) {
throw new ServletException(e);
} finally {
logServices.closeQuietly();
}
}
}
我看来,像你想重新实现的WebSockets。或彗星。 – kaqqao 2014-08-29 18:58:05
如果您试图保持打开状态,请在“持续连接”上进行一些搜索,否则默认情况下,我认为一旦服务器传输完所有数据后应关闭连接。 创建持久连接请参阅http://stackoverflow.com/questions/3304006/persistent-httpurlconnection-in-java – Jason 2014-09-02 23:38:57