web学习02

获取servletConfig对象

ServletConfig对象(每个servlet都有)

获取方式一:

通过ServletConfig对象获取servlet的配置信息

还可以获取多个配置信息

public class Demo01 extends HttpServlet {
	private ServletConfig config;
	@Override
	public void init(ServletConfig config) throws ServletException {
		super.init(config);
		this.config = config;
	}
	
	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		System.out.println(config);
		String value = this.config.getInitParameter("wanglong");
		System.out.println(value);
		Enumeration<String> values = this.config.getInitParameterNames();
		while (values.hasMoreElements()) {
			System.out.println(values.nextElement());
		}
	
}
	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}

}

获取方式二:

直接调用父类的方法

ServletConfig myConfig = this.getServletConfig();
String value = myConfig.getInitParameter("dahai");

域对象

域表示一定的范围内有作用的对象

ServletContext(作用范围最大的域对象) 域对象

作用于整个工程(项目) 都能使用该对象

并且整个项目只有一个该对象是单例对象

作用:利用单例的特点可以进行传值

该对象内部维护了一个map集合

注意:所有的域对象内部都是维护了一个map集合

获取ServletContext对象

先在web-xml添加配置信息:

       <init-param>
  		<param-name>wanglong</param-name>
  		<param-value>znb</param-value>
  	</init-param>
  	<init-param>
  		<param-name>dahai</param-name>
  		<param-value>zsb</param-value>
  	</init-param>

方式1:通过ServletConfig对象来获取

public class Demo02 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		ServletConfig servletConfig = this.getServletConfig();
		ServletContext context = servletConfig.getServletContext();
		context.setAttribute("userName", "wanglong");
		Enumeration<String> attributeNames = context.getAttributeNames();
	    while (attributeNames.hasMoreElements()) {
			System.out.println(attributeNames.nextElement());
		}
}

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

}

方式2: 通过父类来获取该方法在servletConfig

ServletContext context = this.getServletContext();
String value = context.getInitParameter("kuner");
System.out.println(value);

作用:

1.存值取值

2.获取全局配置信息

3.可以获取服务器上所有资源的真实路径

真实路径(在服务器上的路径)getRealPath()

4.可以进行请求转发

获取服务器上的资源路径

路径是相对于工程名来填的文件位置不同路径就不同

读取a文件:a和包同级

	        String contextPath = this.getServletContext().getContextPath();
		String path = this.getServletContext().getRealPath("/WEB-INF/classes/a.properties");
		System.out.println(contextPath);
		System.out.println(path);
		FileInputStream fis = new FileInputStream(path);
		Properties properties = new Properties();
		properties.load(fis);
		System.out.println(properties.getProperty("key"));

b在包下:

String path1 = this.getServletContext().getRealPath("/WEB-INF/classes/com/lanou3g/b.properties");

c在web-inf下:

String path2 = this.getServletContext().getRealPath("/WEB-INF/c.properties");

请求转发

1.用户只发起了一次请求

2.用户请求时并不知道网站内部做了什么操作

通过Context对象获取请求转发器

注意:请求转发只能是站内转发转发的路径是相对于你的工程的

                System.out.println("我是Demo05 借钱");
		RequestDispatcher dispatcher = this.getServletContext().getRequestDispatcher("/demo06");
		dispatcher.forward(request, response);
		System.out.println("钱借到了");

System.out.println("我是Demo06 借给你");

打印:

我是Demo05 借钱

我是Demo06 借给你

钱借到了

响应response

响应行响应的状态码 200 http协议1.1

响应头

告诉浏览器我要做下载的操作

告诉浏览器你需要使用什么编码格式来解析我的响应

响应体响应浏览器的内容

tomcat 默认的编码格式 iso-8859-1

response.setCharacterEncoding("utf-8");

设置响应头(告诉浏览器使用什么格式解析数据)

response.setHeader("Content-type", "text/html;charset=UTF-8");

二合一写法(之后再写servlet 第一个就写这个)

response.setContentType("text/html;charset=utf-8");

接到请求后向浏览器写个字符串

通过响应对象中的流对象回写

reponse.getoutputstream 两者只能用一个

                PrintWriter writer = response.getWriter();
		writer.write("aaa");

从服务器下载图片

1.告诉浏览器图片是下载用的(添加响应头)

2.告诉浏览器文件名字文件类型

public class Demo08 extends HttpServlet{
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		super.doPost(req, resp);
	}
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse response) throws ServletException, IOException {
		ServletContext application =this. getServletContext();
		String path = application.getRealPath("/WEB-INF/classes/tz.png");
		File file =new File(path);
		String name = file.getName();
		byte[] bs= name.getBytes("iso-8859-1");
		response.setHeader("content-disposition", "attachment;filename="+name);
		response.setHeader("content-type", "image/png");

		FileInputStream fis=new FileInputStream(path);
		ServletOutputStream sos = response.getOutputStream();
		int len=0;
		byte[] b=new byte[1024];
		while ((len=fis.read(b))!=-1) {
			sos.write(b, 0, len);
		}
		sos.close();
	}
}

请求重定向响应头

参数时重定向的路径(栈内栈外的网址都可以)

站内的路径带上工程名

注意:请求重定向是两次请求第二次请求是接到了第一次响应头之后发生的

                System.out.println("借钱");
		System.out.println("找demo09");
		resp.setHeader("location", "/sh-web-02/demo10");
		resp.setStatus(302);
		System.out.println("借完了");

System.out.println("haha-demo10");

打印:

借钱

找demo09

借完了

haha-demo10

3秒后跳转一个页面

resp.setHeader("refresh", "3;url=/sh-web-02/demo10");

每隔一秒刷新页面并随机输入数字

                resp.setIntHeader("refresh", 1);
		PrintWriter writer = resp.getWriter();
		writer.write(Math.random()+"");

解决响应乱码

解决请求乱码

response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");

获取请求的方式

String method = request.getMethod();
System.out.println(method);

获取请求的url

StringBuffer url = request.getRequestURL();
System.out.println(url);

获取请求的uri

String uri = request.getRequestURI();
System.out.println(uri);

获取请求网址的相对路径

String contextPath = request.getContextPath();
System.out.println(contextPath);

public class Demo11 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=utf-8");
		request.setCharacterEncoding("utf-8");
		String name = request.getParameter("username");
		String password = request.getParameter("password");
		System.out.println(name);
		System.out.println(password);
		
		String sql="seclect * from users where username=?and password=?";
		Connection connection =null;
		PreparedStatement statement = null;
		 ResultSet resultSet =null;
		try {
			connection= JDBCUtil.getConnection();
		   statement = connection.prepareStatement(sql);
		   statement.setObject(1, name);
		   statement.setObject(2, password);
		   resultSet = statement.executeQuery();
		   while (resultSet.next()) {
			System.out.println("登录成功 欢迎"+name);
		}
		   
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally {
			 //关闭资源
			JDBCUtil.closeAll(resultSet, statement, connection);
		}
	}

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

}

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