day_03 servlet生命周期+servlet编程接口

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servlet的生命周期使用页面进行传参给servlet 通过request读取所有参数

星期四, 十二月 17, 2015 20:53:26

一、servlet生命周期

1.生命全过程

加载 ClassLoader

实例化 new

初始化 init(ServletConfig)

处理请求 service doGet doPost

退出服务 destroy()

2.只有一个对象

3.API中的过程

init()//只执行一次，第一次初始化的时候

service()

destroy()//webapp退出的时候

二、代码案例

servlet类

import java.io.IOException;
import java.io.PrintWriter;

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


public class ServletLifeCycle extends HttpServlet {

	/**
	 * Constructor of the object.
	 */
	public ServletLifeCycle() {
		System.out.println("construct");
	}
	
	/**
	 * Initialization of the servlet. <br>
	 *
	 * @throws ServletException if an error occurs
	 */
	public void init() throws ServletException {
		System.out.println("init");
	}

	/**
	 * Destruction of the servlet. <br>
	 */
	public void destroy() {
		System.out.print("destroy");
	}

	/**
	 * 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 {
			System.out.println("doGet");
	}
}

web.xml

<?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">
  <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>HelloServlet</servlet-name>
    <servlet-class>HelloServlet</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>ServletLifeCycle</servlet-name>
    <servlet-class>ServletLifeCycle</servlet-class>
  </servlet>


  <servlet-mapping>
    <servlet-name>HelloServlet</servlet-name>
    <url-pattern>/httpServlet</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>ServletLifeCycle</servlet-name>
    <url-pattern>/ServletLifeCycle</url-pattern>
  </servlet-mapping>
</web-app>

访问url

http://localhost:8080/TestServlet01/ServletLifeCycle

运行结果:

信息: Server startup in 866 ms

construct

init

doGet

2015-12-17 21:26:10 org.apache.coyote.http11.Http11Protocol pause

信息: Pausing Coyote HTTP/1.1 on http-8080

2015-12-17 21:26:11 org.apache.catalina.core.StandardService stop

信息: Stopping service Catalina

destroy2015-12-17 21:26:11 org.apache.catalina.core.ApplicationContext log

信息: SessionListener: contextDestroyed()

2015-12-17 21:26:11 org.apache.catalina.core.ApplicationContext log

信息: ContextListener: contextDestroyed()

从结果可以看出，先调用construct，然后init且只初始化一次

doGet..doGet可多次调用，最后在tomcat退出的时候，才执行destroy

二_servlet编程接口

1.GenericServlet是所有Servlet的鼻祖

2.用户HTTP的Servlet编程都通过继承。

javax.servlet.http.HttpServlet 实现

3.请求处理方法:

分别对应http协议的7种请求

3.1 doGet 响应Get请求，常用

3.2 doPost 响应Post请求，常用

3.3 doPut 用户http1.1协议

3.4 doDelete 用户http1.1协议

3.5 doHead 仅响应Get请求头部

3.6 doOptions 用户http1.1协议

3.7 doTrace 用于http1.1协议

4.实例个数

在非分布式的情况下，通常一个Servlet在服务器中一个实例

实现3个参数通过doGet()和doPost()传递

代码案例:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>MyHtml.html</title>
  </head>
  
  <body>
    <form method="post" action = "servlet/ThreeParams">
    <table>
    	<tr>
    		<tb width="93">param1</tb>
    		<tb width="94">
    			<input name="param1" type="text" id="param1"/>
    		</tb>
    	</tr>
    	<tr>
    		<tb width="93">param2</tb>
    		<tb width="94">
    			<input name="param2" type="text" id="param2"/>
    		</tb>
    	</tr>
    	<tr>
    		<tb width="93">param3</tb>
    		<tb width="94">
    			<input name="param3" type="text" id="param3"/>
    		</tb>
    	</tr>
    	<br/>
    	<tr>
    		<tb width="94">
    			<input  type="submit"/>
    		</tb>
    	</tr>
    </table>
   </form>
  </body>
</html>	

/TestServlet01/src/ThreeParams.java
servlet类
ThreeParams.java

import java.io.IOException;
import java.io.PrintWriter;

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


public class ThreeParams extends HttpServlet {

	/**
	 * 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 {

		response.setContentType("text/html");
		PrintWriter out = response.getWriter();
		out.println(request.getParameter("param1"));
		out.println("<br/>");
		out.println(request.getParameter("param2"));
		out.println("<br/>");
		out.println(request.getParameter("param3"));
	}

	/**
	 * 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 {
		System.out.print("doPost");
		doGet(request,response);
	}

}

运行结果:

http://localhost:8080/TestServlet01/MyHtml.html

提交后post

http://localhost:8080/TestServlet01/servlet/ThreeParams

console展示

doPost

星期四, 十二月 17, 2015 22:36:55

今天了解了servlet的生命周期

和使用页面进行传参给servlet

星期日, 十二月 20, 2015 19:57:11

07_通过request读取所有参数

7.1代码案例:

http://localhost:8080/TestServlet01/MyHtml.html

MyHtml.html

<html>
    <head>
        <title>A sample show parameters</title>
    </head>
    <body>A sample show parameters
    
        <form method="post" action="servlet/ShowParameters">
            Item Number:<input type="text" name="itemNum"><br>
            Quantity:<input type="text" name="quantity"><br>
            Price each:<input type="text" name="price" value="$"><br>
            First Name:<input type="text" name="firstName"><br>
            Last Name:<input type="text" name="lastName"><br>
            Middle Initial:<input type="text" name="initial"><br>
            
            Shipping Address:<textarea name="address" row="3" cols="40"></textarea><br>
            Credit Card:<br>
            <!--单框示例-->
            &nbsp;&nbsp;<input type="radio" name="cardType" value="Visa">Visa<br>
            &nbsp;&nbsp;<input type="radio" name="cardType" value="Master Card">Master Card<br>
            &nbsp;&nbsp;<input type="radio" name="cardType" value="Amex">Amex<br>
            &nbsp;&nbsp;<input type="radio" name="cardType" value="Discover">Discover<br>
            &nbsp;&nbsp;<input type="radio" name="cardType" value="Java SmartCard">Java SmartCard<br>
            <!--密码输入框-->
            Credit Card password:<input type="password" name="cardNum"><br>
            Repeat Credit Card password:<input type="password" name="cardNum"><br><br>
            <center><input type="submit" value="Submit Order"></center>
        </form>
    </body>
</html>

ShowParameters.java

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

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

public class ShowParameters extends HttpServlet { 
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=gb2312");
        PrintWriter out = response.getWriter();
        
        String title = "Reading All Request Parameters";
        out.println("init");
        out.println("<html><head><title>读取所有参数</title></head>"
                + title
                + "\n" + "<table border=1 align=center>\n"
                + "<TH>Parameter Name<TH>Parameter Value(s)");
        
        // Returns an Enumeration of String objects containing the names of the parameters contained in this request. 
        Enumeration paramNames = request.getParameterNames();
        // Tests if this enumeration contains more elements. 
        while(paramNames.hasMoreElements()) {
            // Returns the next element of this enumeration if this enumeration object has at least one more element to provide. 
            String paraName = (String)paramNames.nextElement();
            out.println("<tr><td>" + paraName + "\n<td>");
            // Returns an array of String objects containing all of the values the given request parameter has, or null if the parameter does not exist. 
            // 注意参数paraName（变量）不能加双引号，否则就是找参数名叫paraName的对应值了。
            String[] paramValues = request.getParameterValues(paraName);
            // 这个参数只有一个值
            if(paramValues.length == 1) {
                String paramValue = paramValues[0];
                if(paramValue.length() == 0) {
                    out.println("<I>no value</I>");
                } else {
                    out.println(paramValue);
                }
            }else {
                // 这个参数有好几条值
                out.println("<UL>");
                for(int i = 0; i < paramValues.length; i++) {
                    out.println("<LI>" + paramValues[i]);
                }
                out.println("</UL>");
            }
        }
        out.println("</table>\n<body></html>");
    } 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("doPost");
        doGet(request,response);
    } 
}

web.xml

<?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">
  <servlet>
    <servlet-name>HelloServlet</servlet-name>
    <servlet-class>HelloServlet</servlet-class>
  </servlet>
  <servlet>
    <servlet-name>ServletLifeCycle</servlet-name>
    <servlet-class>ServletLifeCycle</servlet-class>
  </servlet>
  <servlet>
    <servlet-name>ThreeParams</servlet-name>
    <servlet-class>ThreeParams</servlet-class>
  </servlet>
  <servlet>
    <servlet-name>ShowParameters</servlet-name>
    <servlet-class>ShowParameters</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>HelloServlet</servlet-name>
    <url-pattern>/httpServlet</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>ServletLifeCycle</servlet-name>
    <url-pattern>/ServletLifeCycle</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>ThreeParams</servlet-name>
    <url-pattern>/ThreeParams</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>ShowParameters</servlet-name>
    <url-pattern>/servlet/ShowParameters</url-pattern>
  </servlet-mapping>
</web-app>

十二月 20, 2015 19:59:17

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day_05cookie+session+application | day_02 servlet第一个小程序

2015-12-17 22:40
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