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<title>csdn_Servlet基本结构</title>
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<td WIDTH="50%" bordercolor="#FFFFFF" CLASS="t1" bgcolor="#F0F0F0" align="center" nowrap>Servlet基本结构 </td>
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<span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4">下面的代码显示了一个简单Servlet的基本结构。该Servlet处理的是GET请求，所谓的GET请求，如果你不熟悉HTTP，可以把它看成是当用户在浏览器地址栏输入URL、点击Web页面中的链接、提交没有指定METHOD的表单时浏览器所发出的请求。Servlet也可以很方便地处理POST请求。POST请求是提交那些指定了METHOD="POST"的表单时所发出的请求，具体请参见稍后几节的讨论。
<br>
</span><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4">import
java.io.*;<br>
</span><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4">import
javax.servlet.*;<br>
</span><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4">import
javax.servlet.http.*;<br>
</span><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4">public
class SomeServlet extends HttpServlet {<br>
</span><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4">public
void doGet(HttpServletRequest request,<br>
</span><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4">HttpServletResponse
response) <br>
</span><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4">throws
ServletException, IOException { <br>
</span><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4">//
使用"request"读取和请求有关的信息（比如Cookies） <br>
</span><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4">//
和表单数据 // 使用"response"指定HTTP应答状态代码和应答头 <br>
</span><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4">//
（比如指定内容类型，设置Cookie） <br>
</span><span class="unnamed5"><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4"></span></span><span class="unnamed4">PrintWriter
out = response.getWriter(); <br>
</span><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4">//
使用 "out"把应答内容发送到浏览器 }} <br>
</span><span class="unnamed5"><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4"></span></span><span class="unnamed4">如果某个类要成为Servlet，则它应该从HttpServlet
继承，根据数据是通过GET还是POST发送，覆盖doGet、doPost方法之一或全部。doGet和doPost方法都有两个参数，分别为HttpServletRequest
类型和HttpServletResponse 类型。HttpServletRequest提供访问有关请求的信息的方法，例如表单数据、HTTP请求头等等。HttpServletResponse除了提供用于指定HTTP应答状态（200，404等）、应答头（Content-Type，Set-Cookie等）的方法之外，最重要的是它提供了一个用于向客户端发送数据的PrintWriter
。对于简单的Servlet来说，它的大部分工作是通过println语句生成向客户端发送的页面。 <br>
</span><span class="unnamed5"><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4"></span></span><span class="unnamed4">注意doGet和doPost抛出两个异常，因此你必须在声明中包含它们。另外，你还必须导入java.io包（要用到PrintWriter等类）、javax.servlet包（要用到HttpServlet等类）以及javax.servlet.http包（要用到HttpServletRequest类和HttpServletResponse类）。
<br>
</span><span class="unnamed5"><span class="unnamed5"> </span><span class="unnamed5"><span class="unnamed4"></span></span><span class="unnamed4"></span></span><span class="unnamed4">最后，doGet和doPost这两个方法是由service方法调用的，有时你可能需要直接覆盖service方法，比如Servlet要处理GET和POST两种请求时。
</span><br>
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