案例 servlet的常用对象

要点复习
1 Servlet的定义？
Servlet是Java Servlet的简称，称为小服务程序或服务连接器，用Java编写的服务器端程序，主要功能在于交互式地浏览和修改数据，生成动态Web内容。
狭义的Servlet是指Java语言实现的一个接口，广义的Servlet是指任何实现了这个Servlet接口的类，一般情况下，人们将Servlet理解为后者。
Servlet运行于支持Java的应用服务器中。
从原理上讲，Servlet可以响应任何类型的请求，但绝大多数情况下Servlet只用来扩展基于HTTP协议的Web服务器。最早支持Servlet标准的是JavaSoft的Java Web Server，一些其它的基于Java的Web服务器开始支持标准的Servlet。
2Servlet的定义的四种形式？ public class oneServlet implements Servlet { } //采用接口 public class TwoServlet extends GenericServlet {}//采用继承 public class ThreeServlet extends HttpServlet{}//采用继承 @WebServlet(urlPatterns="/d")
public class fourServlect extends HttpServlet {}采用快键 ALT+/ 在写代码中常用 3 Servlet get与post的区别？第一点：get请求和post请求的区别:
浏览器使用get请求访问servlet服务器的时候doget方法接收
浏览器使用post请求访问servlet服务器的时候dopost方法接收
第二点
get请求所带的数据是拼接在地址上的，地址的长度是有限的，1kb=1024 一个字母2个字节 512字母
post传输数据是不受限制的
第三点
登录功能一律不允许使用get请求给服务器发送数据
浏览器默认为get请求
4 Servlet的周期？ servlet周期
构造方法（创建servlet 对象执行）
Servlet 初始化后调用 init () 方法。
Servlet 调用 service() 方法来处理客户端的请求。
Servlet 销毁前调用 destroy() 方法长时间未访问。
最后，Servlet 是由 JVM 的垃圾回收器进行垃圾回收的。
5 Servlet的注册在哪里？
web.xml文件



OneServlet

com.servlet.OneServlet

4




OneServlet

/a

7 Servlet的常用对象有哪些?
ServletConfig
ServletContext 方法的作用
HttpServlet
HttpServletRequest
HttpServletResponseHttpServletRequest
ServletConfig
获取静态数据的二个方式
在web.xml文件中写

home
二家酒店

方式二
@WebServlet(urlPatterns = "/Servlet2",initParams = {
@WebInitParam(name="aaaa",value="张三"),
@WebInitParam(name="age",value="23"),
@WebInitParam(name="height",value="179cm"),
@WebInitParam(name="weight",value="60kg")
})
public class Servlet2 extends HttpServlet { ServletContext 方法的作用 ServletContext {con 上下文 }
tomcat 服务器为每个项目创建一个对象
ServletContext
1个web项目只有一个ServletContext对象
ServletContext 服务器开始创建结束而消失 ServletContext 作用同一个项目共享数据。
1 共享静态数据
2 共享动态数据写在java代码
3 共享文件数据
* 创建对象
* ServletContext sc=getServletContext();获取对象
* sc.setAttribute("pq", "排球"); 接收对象
* 删除对象 sc.removeAttribute("pq"); HttpServle HttpServlet首先必须读取Http请求的内容。Servlet容器负责创建HttpServlet对象，并把Http请求直接封装到HttpServlet对象中，大大简化了HttpServlet解析请求数据的工作量。HttpServlet容器响应Web客户请求流程如下：

创建项目下图所示

package Aservlet;

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

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.xml.ws.Response;

public class oneServlet  implements Servlet{
	public oneServlet() {
		System.out.println(" Servlet构造方法");
	}

	@Override
	public void destroy() {
		System.out.println("Servlet的销毁，释放cpu");
		
	}

	@Override
	public ServletConfig getServletConfig() {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public String getServletInfo() {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public void init(ServletConfig config) throws ServletException {
		//增加静态数据;到web.html去定义
		
		String a=config.getInitParameter("hont");
		System.out.println(a+"输入值为？？？");
		
		System.out.println("加载数据信息");
		
		Enumeration e=config.getInitParameterNames();
		while (e.hasMoreElements()) {
			String key = (String) e.nextElement();
			String value=config.getInitParameter(key);
			System.out.println(key+"@@@@@@"+value);
			
		}
	}

	
	
	@Override
	public void service(ServletRequest arg0, ServletResponse arg1) throws ServletException, IOException {
		System.out.println("Servlet处于运行状态");
		
		
	}
	

}

package Aservlet;

import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


@WebServlet(urlPatterns = "/TwoServlet",initParams = {
		//增加静态数据的第一个学生
		@WebInitParam(name="a",value="胡一伤悲"),
		@WebInitParam(name="age",value="30岁"),
		@WebInitParam(name="height",value="179cm"),
		@WebInitParam(name="weight",value="60kg")
		
})
public class TwoServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

    
    public TwoServlet() {
        // TODO Auto-generated constructor stub
    }

	
    @Override
    public void init() throws ServletException {
    	// TODO Auto-generated method stub
    	super.init();
    	//定义4个静态数据
    	ServletConfig config=getServletConfig();
    	String a=config.getInitParameter("a");
    	String b=config.getInitParameter("age");
    	String c=config.getInitParameter("height");
    	String e=config.getInitParameter("weight");
    	System.out.println(a+"===="+b+"#######"+c+"-----"+e);
    	System.out.println(e);
    }
 
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//设置 发送给浏览器的文本信息HTML文本格式
		//response.setContentType("text/html");
		response.setContentType("text/html");
		//设置发送给浏览器文本utf-8
		//response.setCharacterEncoding("UTF-8");
		response.setCharacterEncoding("UTF-8");
		//因为浏览器是使用get请求
		//所以Servlet do-get
		//servlet1相打篮球
		//1获取ServletContext对象
		ServletContext  sc=getServletContext();
		//获取web.xml文件中的镜头数据
		String a=sc.getInitParameter("LQ");
		//获得servlet4共享的排球
		String b= (String) sc.getAttribute("PQ");
		//删除排球
		sc.removeAttribute("PQ");
		//给浏览器发送数据
		response.getWriter().append("Servlet1获得静态数据用来访问lq:"+a);
		response.getWriter().append("response.getWriter().append方法打印内容");
		response.getWriter().append("Servlet1获得静态数据用来访问pq:"+b);
		
	}

	
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

package Aservlet;

import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


@WebServlet(urlPatterns = "/TreeServlet",initParams = {
		@WebInitParam(name="aaa",value="胡三定"),
		@WebInitParam(name="age",value="67岁"),
		@WebInitParam(name="height",value="180cm"),
		@WebInitParam(name="weight",value="60kg"),
})
public class TreeServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

    
    public TreeServlet() {
        // TODO Auto-generated constructor stub
    }
    
    @Override
    public void init() throws ServletException {
    	// TODO Auto-generated method stub
    	
    	super.init();
    	ServletConfig config=getServletConfig();
    	String a=config.getInitParameter("aaa");
    	String b=config.getInitParameter("age");
    	String c=config.getInitParameter("height");
    	String e=config.getInitParameter("weight");
    	System.out.println(a+"===="+b+"========"+c+"======="+e);
    }

	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//设置 发送给浏览器的文本信息HTML文本格式
				//response.setContentType("text/html");
				response.setContentType("text/html");
				//设置发送给浏览器文本utf-8
				//response.setCharacterEncoding("UTF-8");
				response.setCharacterEncoding("UTF-8");
				//因为浏览器是使用get请求
				//所以Servlet do-get
				//servlet1相打篮球
				//1获取ServletContext对象
				ServletContext  sc=getServletContext();
				//获取web.xml文件中的镜头数据
				String a=sc.getInitParameter("LQ");
				//给浏览器发送数据
				response.getWriter().append("Servlet3获得静态数据用来访问lq:"+a);
	
	
	}

	
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

package Aservlet;

import java.io.IOException;
import java.io.OutputStream;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


@WebServlet("/fourServlet")
public class fourServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    
    public fourServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//servlet4共享班级 共享数据
		//共享动态数据
		response.setContentType("text/html");
		//设置发送给浏览器文本utf-8
		//response.setCharacterEncoding("UTF-8");
		response.setCharacterEncoding("UTF-8");
		//获取ServletContext 对象
		ServletContext sc=getServletContext();
		//将排球共享数据 setAttribute方法共享数据。
		//在java中object是任何数据类型的父类。
		//身份的多种类型；向上转型
		sc.setAttribute("pq", "排球");
		sc.setAttribute("yq", "羽毛球");
		sc.setAttribute("rd", "读书");
		//身份的多种类型；向上转型(强制转型)
		//获得动态数据
		//疯狂java讲义
		//getimitParameter只能获得静态数据
		 String  a= (String) sc.getAttribute("pq");
		 String  b= (String) sc.getAttribute("yq");
		 String  c= (String) sc.getAttribute("rd");
		
		
		response.getWriter().append("Servlet4获得动态数据 "+a);
		response.getWriter().append("Servlet4获得动态数据 "+b);
		response.getWriter().append("Servlet4获得动态数据 "+c);
	}
	
	

	
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

package Aservlet;

import java.io.IOException;
import java.io.InputStream;
import java.util.Set;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


@WebServlet(urlPatterns = "/FiveServlet5", initParams = {
		// 增加静态数据的第一个学生
		@WebInitParam(name = "a", value = "文件下载"),

})
public class FiveServlet5 extends HttpServlet {
	private static final long serialVersionUID = 1L;

	
	public FiveServlet5() {
		// TODO Auto-generated constructor stub
	}

	
	@Override
	public void init() throws ServletException {
		// TODO Auto-generated method stub
		super.init();
		// 定义4个静态数据
		ServletConfig config = getServletConfig();
		String a = config.getInitParameter("a");
		System.out.println(a);

	}

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html");
		response.setCharacterEncoding("UTF-8");
		// 获得text.txt完整路径
		ServletContext sc = getServletContext();
		// 指定文件名称获取完整路径
		String path = sc.getRealPath("text.txt");
		// 控制台打印输出文件完整路径
		System.out.println(path);


		// 指定文件夹
		Set oSet = sc.getResourcePaths("/WEB-INF");
		for (String string : oSet) {
			System.out.println(string);

		}

		// response.getWriter().append("Served at: ").append(request.getContextPath());

		response.getWriter().append("Servlet1获得静态数据用来访问lq:");
		response.getWriter().append("response.getWriter().append方法打印内容");
		response.getWriter().append("Servlet1获得静态数据用来访问pq:");

	}

	
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

package Aservlet;

import java.awt.image.RescaleOp;
import java.io.IOException;
import java.io.OutputStream;

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


@WebServlet("/SxiServlet")
public class SxiServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
    
    public SxiServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// response  回复  当浏览器根据地址发送请求servlet.servlet 使用response对象回复对象
		//设置servlet发送的数据支撑HTML格式
		response.setContentType("text/html");
		//设置发送servlet 浏览html格式 utf-8
		response.setCharacterEncoding("UTF-8");
		//response  回复  内容/数据/消息
		String info="hellow world java";
		String info1="你好, java jsp";
		
		//使用response获得输出
		OutputStream  os =response.getOutputStream();
		os.write(info.getBytes());
		os.write(info1.getBytes());
		
	}

	
		
	}

package Aservlet;

import java.io.IOException;
import java.io.InputStream;
import java.util.Set;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


@WebServlet(urlPatterns = "/SevenServlet",initParams = {
		//增加静态数据的第一个学生
		@WebInitParam(name="a",value="胡五伤悲"),
		@WebInitParam(name="age",value="47岁"),
		@WebInitParam(name="height",value="169cm"),
		@WebInitParam(name="weight",value="60kg")
		
})
public class SevenServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

    
    public SevenServlet() {
        // TODO Auto-generated constructor stub
    }

	
    @Override
    public void init() throws ServletException {
    	// TODO Auto-generated method stub
    	super.init();
    	//定义4个静态数据
    	ServletConfig config=getServletConfig();
    	String a=config.getInitParameter("a");
    	String b=config.getInitParameter("age");
    	String c=config.getInitParameter("height");
    	String e=config.getInitParameter("weight");
    	System.out.println(a+"===="+b+"#######"+c+"-----"+e);
    	System.out.println(e);
    	System.out.println("创建静态数据的方法");
    	System.out.println("ServletConfig config=getServletConfig();");
    	System.out.println("访问静态数据的方法");
    	System.out.println("String a=config.getInitParameter("a");");
    	
    }
 
   
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html");
		response.setCharacterEncoding("UTF-8");
		// 获得text.txt完整路径
				ServletContext sc=getServletContext();
				//指定文件名称获取完整路径
				String path=sc.getRealPath("A.txt");
				//控制台打印输出文件完整路径
				System.out.println(path);
			//	指定文件夹
			Set oSet=sc.getResourcePaths("/WEB-INF");
			for (String string : oSet) {
				System.out.println(string);
				
			}
			
			//response.getWriter().append("Served at: ").append(request.getContextPath());
				
		
		response.getWriter().append("Servlet1获得静态数据用来访问lq:");
		response.getWriter().append("response.getWriter().append方法打印内容");
		response.getWriter().append("Servlet1获得静态数据用来访问pq:");
		
	}

	
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

运行结果

案例 servlet的常用对象

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