[Java拾遗三]JavaWeb基础之Servlet

1 public class HelloWorldServlet extends HttpServlet {
2     @Override
3     public void doGet(HttpServletRequest req, HttpServletResponse resp)
4             throws ServletException, IOException {
5         System.out.println("hello world servlet");
6     }
7 }

<servlet-mapping>
       <servlet-name>HelloWroldServlet</servlet-name>
       <url-pattern>/helloWorld</url-pattern>
</servlet-mapping>
   
<servlet>
       <servlet-name>LifeServlet</servlet-name>
       <servlet-class>cn.augmentum.b_life.LifeServlet</servlet-class>
</servlet>     

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    ServletConfig conf=this.getServletConfig();
    //获取当前servlet名字
    String name=conf.getServletName();
    System.out.println(name);
    
    //获取名字为 "姓名"的参数值
    String value = conf.getInitParameter("姓名");
    System.out.println(value);
    
    //获取全部参数名称
    Enumeration<String> names=conf.getInitParameterNames();
    while(names.hasMoreElements()){
        String name_=names.nextElement();
        System.out.println(name_+":"+conf.getInitParameter(name_));
    }
}

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //首先获取ServletContext对象
    ServletContext context=this.getServletContext();
    
    //获取url
    String url=context.getInitParameter("url");
    //System.out.println(url);
    
    //获取全部的全局初始化参数
    Enumeration<String> paramNames=context.getInitParameterNames();
    while(paramNames.hasMoreElements()){
        String name=paramNames.nextElement();
        ///System.out.println(name+":"+context.getInitParameter(name));
    }
    
    //返回 "/"的路径
    //String path=context.getRealPath("/");
    //String path = context.getRealPath("/5.txt"); // 错误的
    //System.out.println(path);
    /*InputStream in = context.getResourceAsStream("/WEB-INF/classes/cn/itcast/e_servletcontext/5.txt");
    BufferedReader reader = new BufferedReader(new InputStreamReader(in));
    String readLine = reader.readLine();
    System.out.println(readLine);*/
    
    //获取index.htmlmime类型
    
    String type = context.getMimeType("/a.html");
    //System.out.println(type);
    URL url_ = context.getResource("/a.html");
    System.out.println(url_.getPath());
}

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //String path1 = PathServlet.class.getResource("/").getPath();
    // D:/JavaTools/apache-tomcat-7.0.53/webapps/day09/WEB-INF/classes/
    //String path2 = PathServlet.class.getResource("").getPath();
    // D:/JavaTools/apache-tomcat-7.0.53/webapps/day09/WEB-INF/classes/cn/augmentum/h_classpath/
    // System.out.println(path1);
    // System.out.println(path2);

    //String path3 = PathServlet.class.getClassLoader().getResource("/").getPath();
    //String path4 = PathServlet.class.getClassLoader().getResource("").getPath();

    //System.out.println(path3);
    //System.out.println(path4);
    //       myeclipse                         tomcat路径                                             获取
    //1.txt  src                            /WEB-INF/classes/1.txt                            lei.class.getResource("/").getpath()
    //2.txt  webroot                        /2.txt                                            context.getRealPath
    //3.txt  web-inf                        /WEB-INF/3.txt                                    context.getRealPath
    //4.txt  cn.augmentum.h_classpath            /WEB-INF/classes/cn/augmentum/h_classpath/4.txt    lei.class.getResource("").getpath()
    
    ServletContext context=this.getServletContext();
    String path1 = PathServlet.class.getResource("/1.txt").getPath();
    String path2 = context.getRealPath("/2.txt");
    String path3 = context.getRealPath("/WEB-INF/3.txt");
    String path4 = PathServlet.class.getResource("4.txt").getPath();
    
    /*System.out.println(path1);
    System.out.println(path2);
    System.out.println(path3);
    System.out.println(path4);*/
    readFile(path1);
    readFile(path2);
    readFile(path3);
    readFile(path4);
}

public class CountServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //访问计数
        //首先获取context对象
        ServletContext context=this.getServletContext();
        //请求一次,context取出访问次数
        Integer count=(Integer) context.getAttribute("count");
        //次数+1,放入context中
        if (count==null) {
            context.setAttribute("count", 1);
        }else{
            context.setAttribute("count", ++count);
        }
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

 1 public class ShowServlet extends HttpServlet {
 2 
 3     public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 4         //首先获取context
 5         ServletContext context=this.getServletContext();
 6         //取次数
 7         Integer count=(Integer) context.getAttribute("count");
 8         System.out.println("访问的次数为:"+(count==null?0:count));
 9     }    
10 
11     public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
12         doGet(request, response);
13     }
14 
15 }

<body>
2     <a href="/servletDemo/count">显示次数</a><br/>
3     <a href="/servletDemo/show">展示结果</a><br/>
4 </body>

 1 <servlet>
 2     <servlet-name>CountServlet</servlet-name>
 3     <servlet-class>cn.augmentum.showcount.CountServlet</servlet-class>
 4 </servlet>
 5 <servlet>
 6     <servlet-name>ShowServlet</servlet-name>
 7     <servlet-class>cn.augmentum.showcount.ShowServlet</servlet-class>
 8 </servlet>
 9 <servlet-mapping>
10     <servlet-name>CountServlet</servlet-name>
11     <url-pattern>/count</url-pattern>
12 </servlet-mapping>
13 <servlet-mapping>
14     <servlet-name>ShowServlet</servlet-name>
15     <url-pattern>/show</url-pattern>
16 </servlet-mapping>