servlet中service doGet doPost 的关系
2016-06-15 19:46
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HttpServlet 里的三个方法:service(HttpServletRequest req, HttpServletResponse
resp) ,doGet(HttpServletRequest req, HttpServletResponse resp), doPost(HttpServletRequest req, HttpServletResponse res)的区别和联系:
在servlet中默认情况下,无论你是get还是post 提交过来 都会经过service()方法来处理,然后转向到doGet
或是doPost方法,我们可以查看HttpServlet 类的service方法: 我在tomcat的lib目录下,解压servlet-api.jar,然后用反编译软件把lib\javax\servlet\http下的HttpServlet.class反编译,看里头的service()方法的原代码:
注意,sun只是定义了servlet接口,而实现servlet接口的就是类似于tomcat的服务器,所以我是在tomcat的安装目录下找到实现的类。
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException
{
String method = req.getMethod();
if(method.equals("GET"))
{
long lastModified = getLastModified(req);
if(lastModified == -1L)
{
doGet(req, resp);
} else
{
long ifModifiedSince = req.getDateHeader("If-Modified-Since");
if(ifModifiedSince < (lastModified / 1000L) * 1000L)
{
maybeSetLastModified(resp, lastModified);
doGet(req, resp);
} else
{
resp.setStatus(304);
}
}
} else
if(method.equals("HEAD"))
{
long lastModified = getLastModified(req);
maybeSetLastModified(resp, lastModified);
doHead(req, resp);
} else
if(method.equals("POST"))
doPost(req, resp);
else
if(method.equals("PUT"))
doPut(req, resp);
else
if(method.equals("DELETE"))
doDelete(req, resp);
else
if(method.equals("OPTIONS"))
doOptions(req, resp);
else
if(method.equals("TRACE"))
{
doTrace(req, resp);
} else
{
String errMsg = lStrings.getString("http.method_not_implemented");
Object errArgs[] = new Object[1];
errArgs[0] = method;
errMsg = MessageFormat.format(errMsg, errArgs);
resp.sendError(501, errMsg);
}
}
从上面可以看出 这里的service是用来转向的,但是如果你在自己的servlet类中覆盖了service方法,比如说你的service是这样的:
Java代码
1. public void service(ServletRequest req, ServletResponse res)
2. throws ServletException, IOException {
3. res.getOutputStream().print(
4. "image is <img src='images/downcoin.gif'></img><br>");
5. }
那么这时service就不是用来转向的,而是用来处理业务的,现在不论你的客户端是用pos还是get来请求此servlet
都会执行service方法也只能执行servlet方法,不会去执行doPost或是doGet方法。
比如说:你的客户端代码是:
Java代码
1. <%@page contentType="text/html; charset=utf-8"%>
2. <html>
3. <head><title>选择</title></head>
4. <body>
5. 请选择你喜欢的水果:<br>
6. <form action = "Test" method = "post">
7. <input type="checkbox" name="fruit" value ="apple" >苹果<br>
8. <input type="checkbox" name="fruit" value ="orange">桔子<br>
9. <input type="checkbox" name="fruit" value ="mango">芒果<br>
10. <input type="submit" value="提交">
11. </form>
12. </body>
13. </html>
14.
15. 服务端servlet是:Test类
16.
17. import java.io.IOException;
18.
19. import javax.servlet.ServletException;
20. import javax.servlet.ServletOutputStream;
21. import javax.servlet.ServletRequest;
22. import javax.servlet.ServletResponse;
23. import javax.servlet.http.HttpServlet;
24. import javax.servlet.http.HttpServletRequest;
25. import javax.servlet.http.HttpServletResponse;
26.
27. /**
28. * 演示service方法
29. */
30. public class Test extends HttpServlet {
31.
32. public void service(ServletRequest req, ServletResponse res)
33. throws ServletException, IOException {
34. res.getOutputStream().print("This is the service");
35.
36. }
37.
38. protected void doGet(HttpServletRequest request,
39. HttpServletResponse response) throws ServletException, IOException {
40. doPost(request,response);
41.
42. }
43. protected void doPost(HttpServletRequest request,
44. HttpServletResponse response) throws ServletException, IOException {
45. ServletOutputStream out=response.getOutputStream();
46. String[] args=(String[])request.getParameterValues("fruit");
47. for(int i=0;i<args.length;i++){
48. out.print(args[i]+"<br>");
49. }
50.
51. }
52. }
点击提交后:页面输出结果为“This is the service“;
所以,我们在写servlet的时候,一般都是重写doGet或doPost方法,不会管service方法。
resp) ,doGet(HttpServletRequest req, HttpServletResponse resp), doPost(HttpServletRequest req, HttpServletResponse res)的区别和联系:
在servlet中默认情况下,无论你是get还是post 提交过来 都会经过service()方法来处理,然后转向到doGet
或是doPost方法,我们可以查看HttpServlet 类的service方法: 我在tomcat的lib目录下,解压servlet-api.jar,然后用反编译软件把lib\javax\servlet\http下的HttpServlet.class反编译,看里头的service()方法的原代码:
注意,sun只是定义了servlet接口,而实现servlet接口的就是类似于tomcat的服务器,所以我是在tomcat的安装目录下找到实现的类。
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException
{
String method = req.getMethod();
if(method.equals("GET"))
{
long lastModified = getLastModified(req);
if(lastModified == -1L)
{
doGet(req, resp);
} else
{
long ifModifiedSince = req.getDateHeader("If-Modified-Since");
if(ifModifiedSince < (lastModified / 1000L) * 1000L)
{
maybeSetLastModified(resp, lastModified);
doGet(req, resp);
} else
{
resp.setStatus(304);
}
}
} else
if(method.equals("HEAD"))
{
long lastModified = getLastModified(req);
maybeSetLastModified(resp, lastModified);
doHead(req, resp);
} else
if(method.equals("POST"))
doPost(req, resp);
else
if(method.equals("PUT"))
doPut(req, resp);
else
if(method.equals("DELETE"))
doDelete(req, resp);
else
if(method.equals("OPTIONS"))
doOptions(req, resp);
else
if(method.equals("TRACE"))
{
doTrace(req, resp);
} else
{
String errMsg = lStrings.getString("http.method_not_implemented");
Object errArgs[] = new Object[1];
errArgs[0] = method;
errMsg = MessageFormat.format(errMsg, errArgs);
resp.sendError(501, errMsg);
}
}
从上面可以看出 这里的service是用来转向的,但是如果你在自己的servlet类中覆盖了service方法,比如说你的service是这样的:
Java代码
1. public void service(ServletRequest req, ServletResponse res)
2. throws ServletException, IOException {
3. res.getOutputStream().print(
4. "image is <img src='images/downcoin.gif'></img><br>");
5. }
那么这时service就不是用来转向的,而是用来处理业务的,现在不论你的客户端是用pos还是get来请求此servlet
都会执行service方法也只能执行servlet方法,不会去执行doPost或是doGet方法。
比如说:你的客户端代码是:
Java代码
1. <%@page contentType="text/html; charset=utf-8"%>
2. <html>
3. <head><title>选择</title></head>
4. <body>
5. 请选择你喜欢的水果:<br>
6. <form action = "Test" method = "post">
7. <input type="checkbox" name="fruit" value ="apple" >苹果<br>
8. <input type="checkbox" name="fruit" value ="orange">桔子<br>
9. <input type="checkbox" name="fruit" value ="mango">芒果<br>
10. <input type="submit" value="提交">
11. </form>
12. </body>
13. </html>
14.
15. 服务端servlet是:Test类
16.
17. import java.io.IOException;
18.
19. import javax.servlet.ServletException;
20. import javax.servlet.ServletOutputStream;
21. import javax.servlet.ServletRequest;
22. import javax.servlet.ServletResponse;
23. import javax.servlet.http.HttpServlet;
24. import javax.servlet.http.HttpServletRequest;
25. import javax.servlet.http.HttpServletResponse;
26.
27. /**
28. * 演示service方法
29. */
30. public class Test extends HttpServlet {
31.
32. public void service(ServletRequest req, ServletResponse res)
33. throws ServletException, IOException {
34. res.getOutputStream().print("This is the service");
35.
36. }
37.
38. protected void doGet(HttpServletRequest request,
39. HttpServletResponse response) throws ServletException, IOException {
40. doPost(request,response);
41.
42. }
43. protected void doPost(HttpServletRequest request,
44. HttpServletResponse response) throws ServletException, IOException {
45. ServletOutputStream out=response.getOutputStream();
46. String[] args=(String[])request.getParameterValues("fruit");
47. for(int i=0;i<args.length;i++){
48. out.print(args[i]+"<br>");
49. }
50.
51. }
52. }
点击提交后:页面输出结果为“This is the service“;
所以,我们在写servlet的时候,一般都是重写doGet或doPost方法,不会管service方法。
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