Servlet的實(shí)現(xiàn)方式

• 實(shí)現(xiàn) javax.servlet.Servlet

    @Override
    public void destroy() {}
    @Override
    public ServletConfig getServletConfig() {
        return null;
    }
    @Override
    public String getServletInfo() {
        return null;
    }
    @Override
    public void init(ServletConfig config) throws ServletException {    }
    @Override
    public void service(ServletRequest req, ServletResponse res)
            throws ServletException, IOException {
    }
  

• 繼承 javax.servlet.GenericServlet (其實(shí)就是封裝了ServletConfig的方法)

    public class Demo extends GenericServlet{
    @Override
    public void service(ServletRequest req, ServletResponse res)
            throws ServletException, IOException {
    }
  }
  

• 繼承 javax.servlet.http.HttpServlet (先調(diào)用service方法在調(diào)用doGet或者doPost 如果沒(méi)有覆蓋405哦)

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        super.doGet(req, resp);
    }
  
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        super.doPost(req, resp);
    }
  
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        super.service(req, resp);
    }
  

訪問(wèn)doGet方法但是沒(méi)有重寫(xiě)

生命周期方法
init() 僅僅調(diào)用一次
service() 每次處理請(qǐng)求都會(huì)被調(diào)用
destroy() 服務(wù)器停止之前
實(shí)例化是單利模式，線程不安全。

瀏覽器訪問(wèn)Servlet

• web.xml
  • servlet

  <servlet>
        <servlet-name>demo</servlet-name>
        <servlet-class>com.suse.yuxin.servlet.Demo</servlet-class>
        <load-on-startup>servlet的啟動(dòng)順序 0 服務(wù)器啟動(dòng)就創(chuàng)建</load-on-startup>
    </servlet> 
  

  • servlet-mapping

    <servlet-mapping>
        <servlet-name>demo</servlet-name>
        <url-pattern>/demo</url-pattern>
        <url-pattern>/demo1</url-pattern>  //可以匹配多個(gè)路徑
    </servlet-mapping>
    

ServletConfig(servlet的配置信息[web.xml中該servlet配置信息]將會(huì)被加載進(jìn)去)

<servlet>
        <servlet-name>demo</servlet-name>
        <servlet-class>com.suse.yuxin.servlet.Demo</servlet-class>
        <init-param>
            <param-name>test</param-name>
            <param-value>test</param-value>
        </init-param>
</servlet> 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
config.getServletName(); // demo
config.getInitParameter("test"); // test
config.getServletContext();

ServletContext(一個(gè)項(xiàng)目只有一個(gè)ServletContext)

• 域?qū)ο蠊δ?保存和獲取數(shù)據(jù)
• 獲取應(yīng)用的初始化參數(shù)

   <web-app>
      <context-param>
        <param-name>test</param-name>
        <param-value>test</param-value>
      </context-param>
   </web-app>
  ------------------------------
    getInitParameter("test");
  

• 獲取路徑

     getServletContext().getRealPath("");
  

Response

• 發(fā)送狀態(tài)碼

resp.sendError(404,"沒(méi)有找到資源");//用于發(fā)送404 500等錯(cuò)誤碼
resp.setStatus(302);//用于發(fā)送成功的狀態(tài)碼

- 響應(yīng)頭信息**一般是一個(gè)頭一個(gè)值也有一個(gè)頭多個(gè)值**
```java
resp.setHeader("Refresh","test");//用于單個(gè)值
resp.addHeader("xxx", "value");//用于多個(gè)值

• 重定向

  resp.sendRedirect("/demo1");
  ----------------------------------------
  resp.setHeader("Location", "/demo1");
  resp.setStatus(302);
  

• 輸出流

resp.getOutputStream().write("hello word".getBytes());
resp.getWriter().write("hello word");

- - -
###Request
- 獲取客戶端ip
```java
req.getRemoteAddr(); 

• 獲取請(qǐng)求頭

  req.getHeader(String name);
  //可以使用**refresh**請(qǐng)求頭來(lái)防止倒鏈  refresh 指的是該請(qǐng)求是從哪個(gè)界面?zhèn)鬟^(guò)來(lái)的
  

• 獲取參數(shù)

  req.getParameter("");
  req.getParameterValues("");