Servlet学习笔记（设置servlet的字符集、生命周期、映射配置、数据库连接参数的局部配置）

设置servlet的字符集
servlet是sun公司提供的一门用于开发动态web资源的技术，使用java语言编写的运行在服务器端的程序，通过http超文本传输协议接受和响应来自客户端的请求。
servlet的产生是把“html标记”和“大量的业务处理逻辑”给分开，继续留在html页面的“html标记”就形成了静态网页，而“大量的业务处理逻辑”就放到服务器上形成了servlet；

//设置响应对象的字符集
response.setContentType("text/html;charset=utf-8");
response.setCharacterEncoding("utf-8");

servlet的生命周期

servlet	流程
实例化	servlet容器调用构造器创建servlet的实例
初始化	改容器调用init()方法进行初始化
服务	调用doGet()方法响应用户的请求
销毁	服务器停止前调用destory()方法销毁实例
不可用	销毁实例并标记为垃圾，等待垃圾回收机制的回收

Tomcat 与 Servlet 是如何工作的：
Web Client 向Servlet容器（Tomcat）发出Http请求
Servlet容器接收Web Client的请求
Servlet容器创建一个HttpRequest对象，将Web Client请求的信息封装到这个对象中。
Servlet容器创建一个HttpResponse对象
Servlet容器调用HttpServlet对象的service方法，把HttpRequest对象与HttpResponse对象作为参数传给 HttpServlet 对象。
HttpServlet调用HttpRequest对象的有关方法，获取Http请求信息。
HttpServlet调用HttpResponse对象的有关方法，生成响应数据。
servlet的映射配置
由于客户端是通过url地址访问web服务器中的资源，所以servlet程序想被外界访问，必须把servlet程序映射到一个url地址上，这个工作在web.xml文件中使用和完成。

注册servlet
<servlet>
    <servlet-name>Servlet1</servlet-name>
    <servlet-class>com.offcn.study.Servlet1</servlet-class>
  </servlet>
映射一个已注册的servlet的一个对外访问路径
  <servlet-mapping>
    <servlet-name>Servlet1</servlet-name>
    <url-pattern>/study/Servlet1</url-pattern>
  </servlet-mapping>

servlet程序（将访问数据库参数写在代码中）

package com.offcn.study;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class AddCustomer extends HttpServlet {
	/**
	 * Constructor of the object.
	 */
	public AddCustomer() {
		super();
	}

	/**
	 * Destruction of the servlet. <br>
	 */
	public void destroy() {
		super.destroy(); // Just puts "destroy" string in log
		// Put your code here
	}

	/**
	 * The doGet method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to get.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String driver = "com.mysql.jdbc.Driver";
		String url = "jdbc:mysql://localhost:3306/copy";
		String user= "root";
		String password = "root";
		Connection con = null;
		Statement st = null;
		String msg = "";
		
		try {
			Class.forName(driver);
			con = DriverManager.getConnection(url, user, password);
			String sql ="insert into customer(cid,cname,cpassword,mobile) values('C99','咕咚','3639','78945612')";
			st = con.createStatement();
			int iCount = st.executeUpdate(sql);
			msg=iCount>0?"执行成功":"执行失败";
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			try {
				if(st!=null){
					st.close();
				}
				if(con!=null){
					con.close();
				}
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			response.setContentType("text/html;charset=utf-8");
			PrintWriter out = response.getWriter();
			out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
			out.println("<HTML>");
			out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
			out.println("  <BODY>");
			out.println("<p>"+msg+"</p>");
			out.println("  </BODY>");
			out.println("</HTML>");
			out.flush();
			out.close();
		}
		
	}

	/**
	 * The doPost method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to post.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.setContentType("text/html");
		PrintWriter out = response.getWriter();
		out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
		out.println("<HTML>");
		out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
		out.println("  <BODY>");
		out.print("    This is ");
		out.print(this.getClass());
		out.println(", using the POST method");
		out.println("  </BODY>");
		out.println("</HTML>");
		out.flush();
		out.close();
	}

	/**
	 * Initialization of the servlet. <br>
	 *
	 * @throws ServletException if an error occurs
	 */
	public void init() throws ServletException {
		// Put your code here
	}

}

将数据库连接参数局部配置在配置文件中（web.xml）

配置文件中的代码

<servlet>
    <servlet-name>AddCustomer</servlet-name>
    <servlet-class>com.offcn.study.AddCustomer</servlet-class>
    <init-param>
    <param-name>driver</param-name>
    <param-value>com.mysql.jdbc.Driver</param-value>
    </init-param>
    <init-param>
    <param-name>url</param-name>
    <param-value>jdbc:mysql://localhost:3306/copy</param-value>
    </init-param>
    <init-param>
    <param-name>uer</param-name>
    <param-value>root</param-value>
    </init-param>
    <init-param>
    <param-name>password</param-name>
    <param-value>root</param-value>
    </init-param>
  </servlet>

servlet中需要从web.xml中获取连接参数，用servlet对象的ServletConfig对象。

		String driver = "";
		String url = "";
		String user= "";
		String password = "";
		ServletConfig config = this.getServletConfig();//获取ServletConfig对象
		driver= config.getInitParameter("driver");//调用方法，使用名字获取参数
		url = config.getInitParameter("url");
		user = config.getInitParameter("user");
		password = config.getInitParameter("password");

Servlet学习笔记（设置servlet的字符集、生命周期、映射配置、数据库连接参数的局部配置）

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