ServletConfig和ServletContext

ServletConfig对象

## 使用getServletConfig方法创建对象,并在配置文件进行初始化配置 ##
//ServletConfig程序,读取配置文件
`package com.heima.test;

import java.io.IOException;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ServletConfig01 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
ServletConfig config = getServletConfig();
String username = config.getInitParameter("username");
String password = config.getInitParameter("password");
System.out.println(username + " " + password);

}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}`

//配置文件xml
`<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
<display-name></display-name>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>ServletConfig</servlet-name>
<servlet-class>com.heima.test.ServletConfig01</servlet-class>
<init-param> <param-name>username</param-name><param-value>root</param-value> </init-param>
<init-param> <param-name>password</param-name><param-value>123</param-value> </init-param>
</servlet>
<servlet-mapping>
<servlet-name>ServletConfig</servlet-name>
<url-pattern>/demo1</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>`

ServletContext对象

## 使用getServletContext方法创建对象,配置文件xml ##
# 代码实现统计访问网站次数   #
//配置文件
`<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <display-name></display-name>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>ServletCount</servlet-name>
<servlet-class>com.heima.test.ServletCount</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>ServletShow</servlet-name>
<servlet-class>com.heima.test.ServletShow</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>ServletCount</servlet-name>
<url-pattern>/count</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>ServletShow</servlet-name>
<url-pattern>/show</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
`

//统计次数代码
`package com.heima.test;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ServletCount extends HttpServlet {

@Override
public void init() throws ServletException {
ServletContext context = getServletContext();
context.setAttribute("num", 0);
}

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
ServletContext context = getServletContext();
int num = (Integer) context.getAttribute("num");
context.setAttribute("num", num+1);
response.getWriter().write("welcome to website");
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}

}
`

//显示次数代码
`package com.heima.test;

import java.io.IOException;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ServletShow extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
ServletContext context = getServletContext();
int num = (Integer) context.getAttribute("num");
response.getWriter().write("times:" + num);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}

}
`