提问人：overexchange 提问时间：5/31/2015 更新时间：3/15/2021 访问量：26782
HttpServlet 类中的“service”方法是什么？
What is 'service' method in HttpServlet class?
问：
下面是一个为学习而编写的简单 servlet。
package com.example.tutorial;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ServletExample extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PrintWriter out = response.getWriter();
out.println("Hello Java!");
}
}
当浏览器命中此 URI 时： ，http://localhost:8081/ServletsJSPExample/servletexample
通过分析http数据包的请求头，显示浏览器发送的请求。但是，在我的servlet中，我没有要处理的请求。GETGET
所以
何时调用方法？service
为什么方法会收到此请求？serviceGET
答：
25赞
Sotirios Delimanolis
5/31/2015
#1
HttpServlet实现其服务方法 javadoc 状态Servlet
由 servlet 容器调用，以允许 servlet 响应 请求。
这是所有 Servlet 处理的入口点。Servlet 容器实例化您的类，并在生成的实例上调用此方法，如果它确定您应该处理请求。ServletServlet
HttpServlet是一个类，它通过委托给相应的 、 、 方法来实现此方法，具体取决于请求中使用的 HTTP 方法。abstractdoGetdoPostdoXyz
@Override
public void service(ServletRequest req, ServletResponse res)
throws ServletException, IOException
{
HttpServletRequest request;
HttpServletResponse response;
if (!(req instanceof HttpServletRequest &&
res instanceof HttpServletResponse)) {
throw new ServletException("non-HTTP request or response");
}
request = (HttpServletRequest) req;
response = (HttpServletResponse) res;
service(request, response);
}
[...]
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException
{
String method = req.getMethod();
if (method.equals(METHOD_GET)) {
long lastModified = getLastModified(req);
if (lastModified == -1) {
// servlet doesn't support if-modified-since, no reason
// to go through further expensive logic
doGet(req, resp);
} else {
long ifModifiedSince = req.getDateHeader(HEADER_IFMODSINCE);
if (ifModifiedSince < lastModified) {
// If the servlet mod time is later, call doGet()
// Round down to the nearest second for a proper compare
// A ifModifiedSince of -1 will always be less
maybeSetLastModified(resp, lastModified);
doGet(req, resp);
} else {
resp.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
}
}
} else if (method.equals(METHOD_HEAD)) {
long lastModified = getLastModified(req);
maybeSetLastModified(resp, lastModified);
doHead(req, resp);
} else if (method.equals(METHOD_POST)) {
doPost(req, resp);
} else if (method.equals(METHOD_PUT)) {
doPut(req, resp);
} else if (method.equals(METHOD_DELETE)) {
doDelete(req, resp);
} else if (method.equals(METHOD_OPTIONS)) {
doOptions(req,resp);
} else if (method.equals(METHOD_TRACE)) {
doTrace(req,resp);
} else {
//
// Note that this means NO servlet supports whatever
// method was requested, anywhere on this server.
//
String errMsg = lStrings.getString("http.method_not_implemented");
Object[] errArgs = new Object[1];
errArgs[0] = method;
errMsg = MessageFormat.format(errMsg, errArgs);
resp.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED, errMsg);
}
}
如果覆盖 中的方法，则会丢失该行为并恢复到对所有 Servlet 请求的单个处理。serviceHttpServlet
评论
This is an HTTP-specific version of the Servlet.service method, which accepts HTTP specific parameters. This method is rarely overridden. Standard HTTP requests are supported by dispatching to Java methods specialized to implement them.这是来自javadoc的模糊答案