0310 HttpServletRequest

回顾一下 servlet运行流程

通过request获得请求行

获得客户端的请求方式：String getMethod()

获得请求的资源:

获取请求地址uri: String getRequestURI()

获取请求地址url:StringBuffer getRequestURL()

获取去web应用名称:String getContextPath()

获取get请求提交的参数:String getQueryString()

获取客户端的IP地址:getRemoteAddr()

代码展示

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="/WEB04/LineServlet" method="get">
	用户名：<input type="text" name="uname"><br>
	密码：<input type="password" name="pwd"><br>
	爱好：
	足球：<input type="checkbox" name="hobby" value="zq">
	篮球：<input type="checkbox" name="hobby" value="lq">
	乒乓球：<input type="checkbox" name="hobby" value="ppq"><br>
	<input type="submit" value="注册">
</form>
</body>
</html>

　　LineServlet

public class LineServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//获取哦请求方式
		String method=request.getMethod();
		System.out.println("请求方式"+method);
		//获取请求地址uri
		String uri=request.getRequestURI();
		System.out.println("请求地址uri:"+uri);
		//获取请求地址
		StringBuffer url=request.getRequestURL();
		System.out.println("请求地址url是："+url);
		//获取去web应用名称
		String name=request.getContextPath();
		System.out.println("web应用名称是："+name);
		//获取get请求提交的参数
		String query=request.getQueryString();
		System.out.println("get请求提交的参数"+query);
		//获取客户端的IP地址
		String ip=request.getRemoteAddr();
		System.out.println("客户端IP地址是："+ip);	
	}

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

如果jsp文件的提交方式改成post那么这个get请求提交参数就是null

通过request获得请求头

String getHeader();

referer头的作用：获取该访问的的来源

代码展示

public class HeadServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//获取refer头
		String refer=request.getHeader("referer");
		System.out.println(refer);
	}

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

　　还是使用register.jsp的代码将action中的路径改成/WEB04/HeadServlet

referer头可以做一个防盗链的作用就是可以判断这个访问来自哪里如果不是我指定的访问路径就不让他链接

代码展示

referer.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<a href="/WEB04/RefererServlet">14天交易日A股暴跌30%</a>
</body>
</html>

public class RefererServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//获取referer头
		String refer=request.getHeader("referer");
		//解决响应乱码
		response.setContentType("text/html;charset=utf-8");
		if(refer.startsWith("http://localhost")){
			response.getWriter().write("这是一跳爆炸新闻");
		}else{
			response.getWriter().write("到连着 可耻");
		}
	}

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

通过request获得请求体

获取请求体:

String getParameter(String key);

String[] getParameterValues(String name)

Map<String, String[]> getParameterMap()

解决post请求乱码

setCharacterEncoding("UTF-8") 指定码表

解决get 请求乱码

当客户端提交中文，那么先将数据提交，请求行会按照ISO8859-1码表进行解析存到 request对象中然后再传到服务器进行解析，因为服务器是utf-8码表所以解析不出来，所以就会响应给客户端一个乱码，这个解决这个乱码，我们可以再按照这个编码给他编译回去。

运用到

getbytes（“码表”）可以指定码表

new String（bytes,"码表"）也可以指定码表

例：new String(parameter.getbytes("iso8859-1"),"utf-8")

代码展示

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="/WEB04/BodyServlet" method="post">
	用户名：<input type="text" name="uname"><br>
	密码：<input type="password" name="pwd"><br>
	爱好：
	足球：<input type="checkbox" name="hobby" value="zq">
	篮球：<input type="checkbox" name="hobby" value="lq">
	乒乓球：<input type="checkbox" name="hobby" value="ppq"><br>
	<input type="submit" value="注册">
</form>
</body>
</html>

public class BodyServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//解决post请求乱码
		request.setCharacterEncoding("UTF-8");
		//获取请求体
		String uname=request.getParameter("uname");
		//解决get请求乱码
		//uname=new String(uname.getBytes("ISO8859-1"),"UTF-8");
		System.out.println("用户名"+uname);
		String pwd=request.getParameter("pwd");
		System.out.println("密码"+pwd);
		String[] hobbys=request.getParameterValues("hobby");
		for(String s:hobbys){
			System.out.println(s);
		}
		//获取所有参数所在的map集合
		Map<String, String[]> map=request.getParameterMap();
		//获取所有key躲在的set集合
		Set<String> keys=map.keySet();
		for(String key:keys){
			System.out.print(key+":");
			String[] values=map.get(key);
			for(String value:values){
				System.out.print(value+" ");
			}
			System.out.println();
		}
	}

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

因为在上述代码中只解决了第一个name的乱码并没有解决下边的那个map集合中的中文乱码。

request其他功能

request是一个域对象

request对象也是一个存储数据的区域对象、

setAttribute(String name,Object j)

getAttribute(String name)

removeAttribute(String name)

注意：request域的作用范围：一次请求中

request完成请求转发

getRequestDispatcher(String path)方法获得一个RequestDispatcher转发器对象，通过调用RequestDispatcher对象的forward(ServletRequest request, ServletResponse response)方法完成请求转发

代码展示

public class Servlet01 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//request域中存值
		request.setAttribute("name", "张三");
		//请求转发
		//获取请求转发器调用转发方法
		request.getRequestDispatcher("/Servlet02").forward(request, response);;
		
	}

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

public class Servlet02 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
		response.setContentType("text/html;charset=UTF-8");
		//取值
		String name=(String)request.getAttribute("name");
		response.getWriter().write("hello"+name);
	}

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

request域与ServletContext域的区别

request作用域是一次请求中，请求时创建，请求结束销毁

ServletContext作用域是整个项目文件，服务器开启状态部署文件时创建，服务器关闭销毁

重定向与请求转发区别

重定向是请求两次，地址栏改变，不能够传递数据，可以用于访问外部资源。

请求转发是请求一次，地址栏不改变，可以数据传递，只能访问内部资源

图解