Servlet笔记4--ServletConfig接口和ServletContext接口
2017-02-06 14:39
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ServletConfig接口：
ServletContext接口：
代码详解：
（1）web.xml配置文件：
（2） 前端页面：
（3）辅助实体类：
（4） Servlet程序：
ServletContext接口：
代码详解：
（1）web.xml配置文件：
1 <?xml version="1.0" encoding="UTF-8"?> 2 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 3 xmlns="http://java.sun.com/xml/ns/javaee" 4 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 5 id="WebApp_ID" version="2.5"> 6 7 <!-- web.xml文件中配置上下文参数，这些信息被自动封装到ServletContext对象中 --> 8 <context-param> 9 <param-name>username</param-name> 10 <param-value>admin</param-value> 11 </context-param> 12 13 <context-param> 14 <param-name>password</param-name> 15 <param-value>123</param-value> 16 </context-param> 17 18 <servlet> 19 <servlet-name>a</servlet-name> 20 <servlet-class>com.bjpowernode.javaweb.servlet.AServlet</servlet-class> 21 <!-- 初始化参数：被封装到ServletConfig对象中 --> 22 <init-param> 23 <param-name>driver</param-name> 24 <param-value>com.mysql.jdbc.Driver</param-value> 25 </init-param> 26 <init-param> 27 <param-name>url</param-name> 28 <param-value>jdbc:mysql://localhost:3306/bipowernode</param-value> 29 </init-param> 30 <init-param> 31 <param-name>user</param-name> 32 <param-value>root</param-value> 33 </init-param> 34 <init-param> 35 <param-name>password</param-name> 36 <param-value>123</param-value> 37 </init-param> 38 </servlet> 39 <servlet-mapping> 40 <servlet-name>a</servlet-name> 41 <url-pattern>/a</url-pattern> 42 </servlet-mapping> 43 44 <servlet> 45 <servlet-name>b</servlet-name> 46 <servlet-class>com.bjpowernode.javaweb.servlet.BServlet</servlet-class> 47 </servlet> 48 <servlet-mapping> 49 <servlet-name>b</servlet-name> 50 <url-pattern>/b</url-pattern> 51 </servlet-mapping> 52 </web-app>
（2） 前端页面：
1 <html> 2 <head> 3 <title>ServletConfig接口</title> 4 </head> 5 <body> 6 <a href="/prj-servlet-04/a">AServlet</a> 7 <br><br> 8 <a href="/prj-servlet-04/b">BServlet</a> 9 </body> 10 </html>
（3）辅助实体类：
1 package com.bjpowernode.javaweb.entity;
2
3 public class User {
4
5 private String usercode;
6 private String username;
7
8 public String getUsercode() {
9 return usercode;
10 }
11
12 public void setUsercode(String usercode) {
13 this.usercode = usercode;
14 }
15
16 public String getUsername() {
17 return username;
18 }
19
20 public void setUsername(String username) {
21 this.username = username;
22 }
23
24 @Override
25 public String toString() {
26 return "User [usercode=" + usercode + ", username=" + username + "]";
27 }
28
29 }（4） Servlet程序：
1 package com.bjpowernode.javaweb.servlet;
2
3 import java.io.IOException;
4 import java.io.PrintWriter;
5 import java.util.Date;
6 import java.util.Enumeration;
7
8 import javax.servlet.Servlet;
9 import javax.servlet.ServletConfig;
10 import javax.servlet.ServletContext;
11 import javax.servlet.ServletException;
12 import javax.servlet.ServletRequest;
13 import javax.servlet.ServletResponse;
14
15 import com.bjpowernode.javaweb.entity.User;
16
17 public class AServlet implements Servlet {
18
19 private ServletConfig config;
20
21 public void init(ServletConfig config) throws ServletException {
22 this.config = config;
23 }
24
25 public void service(ServletRequest request, ServletResponse response)
26 throws ServletException, IOException {
27
28 response.setContentType("text/html;charset=UTF-8");
29 PrintWriter out = response.getWriter();
30
31 //获取ServletConfig
32 ServletConfig config = getServletConfig();
33
34 //获取Servlet Name
35 String servletName = config.getServletName();
36 out.print("<servlet-name>" + servletName + "</servlet-name>" + "<br><br>");
37
38 //获取ServletContext,后面讲什么是ServletContext
39 ServletContext application = config.getServletContext();
40 out.print("ASevlet's ServletContext = " + application + "<br><br>");
41
42 //通过当前Servlet初始化参数的name获取value
43 /*String driver = config.getInitParameter("driver");
44 String url = config.getInitParameter("url");
45 String user = config.getInitParameter("user");
46 String password = config.getInitParameter("password");*/
47
48 //获取当前Servlet所有初始化参数的name,然后再根据name获取value
49 @SuppressWarnings("unchecked")
50 Enumeration<String> anames = config.getInitParameterNames();
51 out.print("AServlet: <br>");
52 while(anames.hasMoreElements()){
53 String name = anames.nextElement();
54 String value = config.getInitParameter(name);
55 out.print(name + "=" + value);
56 out.print("<br>");
57 }
58 out.print("<br>");
59
60 //获取所有上下文（即当前Servlet的四周环境）初始化参数的name,然后再根据name获取value
61 @SuppressWarnings("unchecked")
62 Enumeration<String> snames = application.getInitParameterNames();
63 out.print("ServletContext: <br>");
64 while(snames.hasMoreElements()) {
65 String name = snames.nextElement();
66 String value = application.getInitParameter(name);
67 out.print(name + "=" + value);
68 out.print("<br>");
69 }
70 out.print("<br>");
71
72 //获取文件绝对路径，参数必须是WebRoot的下一级目录开始写
73 String realPath = application.getRealPath("/WEB-INF/resources/db.properties");
74 out.print(realPath + "<br>");
75
76 //创建User对象
77 User user = new User();
78 user.setUsercode("1231");
79 user.setUsername("jackson");
80
81 //向ServletContext范围中存储User数据
82 application.setAttribute("userObj", user);
83 application.setAttribute("time", new Date());
84
85 }
86
87 public void destroy() {
88
89 }
90
91 public ServletConfig getServletConfig() {
92 return config;
93 }
94
95 public String getServletInfo() {
96 return null;
97 }
98
99
100 }1 package com.bjpowernode.javaweb.servlet;
2
3 import java.io.IOException;
4 import java.io.PrintWriter;
5
6 import javax.servlet.Servlet;
7 import javax.servlet.ServletConfig;
8 import javax.servlet.ServletContext;
9 import javax.servlet.ServletException;
10 import javax.servlet.ServletRequest;
11 import javax.servlet.ServletResponse;
12
13 public class BServlet implements Servlet {
14
15 private ServletConfig config;
16
17 public void init(ServletConfig config) throws ServletException {
18 this.config = config;
19 }
20
21 public void service(ServletRequest request, ServletResponse response)
22 throws ServletException, IOException {
23
24 response.setContentType("text/html;charset=UTF-8");
25 PrintWriter out = response.getWriter();
26
27 //init的时候已经获取过了config
28 out.println("BServlet's ServletConfig = " + config + "<br>");
29
30 ServletContext application = config.getServletContext();
31
32 Object obj1 = application.getAttribute("userObj");
33 Object obj2 = application.getAttribute("time");
34 out.print(obj1 + "<br>");
35 out.print(obj2 + "<br>");
36 }
37
38 public void destroy() {
39
40 }
41
42 public ServletConfig getServletConfig() {
43 return config;
44 }
45
46 public String getServletInfo() {
47 return null;
48 }
49
50
51 }
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