javaweb

http响应

服务器 -- 响应 -- 客户端

Accept：告诉浏览器它所支持的数据类型

Accept-Encoding：支持那种 编码格式  GBK  UTF-8  GB2312  ISO8859-1

Content-Type：text/html   类型

Content-Type: image/png

Connection：keep-Alive   连接

Cache-Control： private  缓存控制

Content-Encoding：gzip   编码

Host：主机……/.

Refresh ：告诉客户端多久刷新一次

Location：让网页重新定位

servlet

web.xml

<?xml version="1.0" encoding="UTF-8" ?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"

         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee

                            http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"

         version="4.0"

         metadata-complete="true">

<servlet>

    <servlet-name>hello</servlet-name>

    <servlet-class>day1.ServletDemo</servlet-class>

</servlet>

    <servlet-mapping>

        <servlet-name>hello</servlet-name>

        <url-pattern>/hello</url-pattern>

    </servlet-mapping>

</web-app>


package day1;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

import java.io.PrintWriter;

public class ServletDemo extends HttpServlet

{

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //ServletInputStream inputStream = req.getInputStream();

        PrintWriter writer = resp.getWriter();

        writer.println("hello world!");

    }

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        this.doGet(req, resp);

    }

}



<?xml version="1.0" encoding="UTF-8" ?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"

         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee

                            http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"

         version="4.0"

         metadata-complete="true">

    <!--    注册servlet-->

<servlet>

    <servlet-name>hello</servlet-name>

    <servlet-class>day1.ServletDemo</servlet-class>

</servlet>

<!--    可以有多个servlet映射-->

    <servlet-mapping>

        <servlet-name>hello</servlet-name>

        <url-pattern>/hello1</url-pattern>

    </servlet-mapping>

    <servlet-mapping>

        <servlet-name>hello</servlet-name>

        <url-pattern>/hello2</url-pattern>

    </servlet-mapping>

    <servlet-mapping>

        <servlet-name>hello</servlet-name>

        <url-pattern>/hello3/*</url-pattern>

<!--        映射可以使用统配符-->

    </servlet-mapping>

</web-app>


<?xml version="1.0" encoding="UTF-8" ?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"

         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee

                            http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"

         version="4.0"

         metadata-complete="true">

<!--    注册servlet-->

<servlet>

    <servlet-name>hello</servlet-name>

    <servlet-class>day1.ServletDemo</servlet-class>

</servlet>

<!--    可以有多个servlet映射-->

    <servlet-mapping>

        <servlet-name>hello</servlet-name>

        <url-pattern>/hello1</url-pattern>

    </servlet-mapping>

    <servlet-mapping>

        <servlet-name>hello</servlet-name>

        <url-pattern>/hello2</url-pattern>

    </servlet-mapping>

    <servlet-mapping>

        <servlet-name>hello</servlet-name>

        <url-pattern>/hello3/*</url-pattern>

<!--        映射可以使用统配符-->

    </servlet-mapping>

    <servlet>

        <servlet-name>error</servlet-name>

        <servlet-class>day1.ErrorServlet</servlet-class>

    </servlet>

    <servlet-mapping>

        <servlet-name>error</servlet-name>

        <url-pattern>/*</url-pattern>

    </servlet-mapping>

</web-app>

优先级问题，指定的固有的映射路径优先级最高，如果找不到就会走默认的处理请求

servlet使用

<?xml version="1.0" encoding="UTF-8" ?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"

         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee

                            http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"

         version="4.0"

         metadata-complete="true">

<servlet>

  <servlet-name>test</servlet-name>

  <servlet-class>test.ContextTest</servlet-class>

</servlet>

  <servlet-mapping>

    <servlet-name>test</servlet-name>

    <url-pattern>/test</url-pattern>

  </servlet-mapping>

  <servlet>

    <servlet-name>test1</servlet-name>

  <servlet-class>test.Test</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>test1</servlet-name>

    <url-pattern>/test1</url-pattern>

  </servlet-mapping>

</web-app>


package test;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

public class ContextTest extends HttpServlet {

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        this.doGet(req, resp);

    }

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

//        this.getServletConfig()//获取servlet配置

        //this.getInitParameter()//获得servlet初始化参数

        ServletContext servletContext = this.getServletContext();

        servletContext.setAttribute("username","王涛");

    }

}


package test;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

import java.io.PrintWriter;

public class Test extends HttpServlet {

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        this.doGet(req, resp);

    }

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        resp.setContentType("text/html");

        resp.setCharacterEncoding("utf8");

        PrintWriter writer = resp.getWriter();

        ServletContext servletContext = this.getServletContext();

        Object username = servletContext.getAttribute("username");

        writer.println(username.toString());

        writer.close();

    }

}

文件过滤问题

<resources>

      <resource>

        <directory>src/main/resources</directory>

        <includes>

          <include>**/*.properties</include>

          <include>**/*.xml</include>

        </includes>

        <filtering>true</filtering>

      </resource>

      <resource>

        <directory>src/main/java</directory>

        <includes>

          <include>**/*.properties</include>

          <include>**/*.xml</include>

        </includes>

        <filtering>true</filtering>

      </resource>

    </resources>

HttpServletRequest

获取前端传递参数
package com.test;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

public class LoginServlet extends HttpServlet {

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        String username = req.getParameter("username");

        String password = req.getParameter("password");

        String[] hobbys = req.getParameterValues("hobbys");

        for (String hobby : hobbys) {

            System.out.println(hobby);

        }

req.getRequestDispatcher("/success.jsp").forward(req,resp);

    }

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        this.doPost(req, resp);

    }

}


<h2>Hello World!</h2>

<div style="text-align: center;">

    <form method="post" action="${pageContext.request.contextPath}/login">

        username: <input type="text" name="username">

        password: <input type="password" name="password">

        hobby:

        <input type="checkbox" name="hobbys" value="girl"> girl

        <input name="hobbys" type="checkbox" value="encoding"> encoding

        <input name="hobbys" type="checkbox" value="song"> song

        <input type="checkbox" name="hobbys" value="playboy"> playboy

<br>

        <input type="submit">

    </form>

</div>

307

HttpServletResponse

响应

web服务器接受到客户端的http请求，针对这个请求，分别创建一个代表响应的HttpServletResponse对象，代表请求的HttpServletRequest对象，

请求来的信息找HttpServletRequest，响应回去的信息找HttpServletResponse

简单分类

负责向浏览器发送数据的方法

public ServletOutputStream getOutputStream() throws IOException;

    public PrintWriter getWriter() throws IOException;

负责向浏览器发送响应头的方法

public void setCharacterEncoding(String charset);

public void setContentLength(int len);

public void setContentLengthLong(long len);

public void setContentType(String type);

public void setBufferSize(int size);

public int getBufferSize();

public void setDateHeader(String name, long date);

    public void addDateHeader(String name, long date);

    public void setHeader(String name, String value);

    public void addHeader(String name, String value);

    public void setIntHeader(String name, int value);

    public void addIntHeader(String name, int value);

    public void setStatus(int sc);


public static final int SC_CONTINUE = 100;

    public static final int SC_SWITCHING_PROTOCOLS = 101;

    public static final int SC_OK = 200;

    public static final int SC_CREATED = 201;

    public static final int SC_ACCEPTED = 202;

    public static final int SC_NON_AUTHORITATIVE_INFORMATION = 203;

    public static final int SC_NO_CONTENT = 204;

    public static final int SC_RESET_CONTENT = 205;

    public static final int SC_PARTIAL_CONTENT = 206;

    public static final int SC_MULTIPLE_CHOICES = 300;

    public static final int SC_MOVED_PERMANENTLY = 301;

    public static final int SC_MOVED_TEMPORARILY = 302;

    public static final int SC_FOUND = 302;

    public static final int SC_SEE_OTHER = 303;

    public static final int SC_NOT_MODIFIED = 304;

    public static final int SC_USE_PROXY = 305;

    public static final int SC_TEMPORARY_REDIRECT = 307;

    public static final int SC_BAD_REQUEST = 400;

    public static final int SC_UNAUTHORIZED = 401;

    public static final int SC_PAYMENT_REQUIRED = 402;

    public static final int SC_FORBIDDEN = 403;

    public static final int SC_NOT_FOUND = 404;

    public static final int SC_METHOD_NOT_ALLOWED = 405;

    public static final int SC_NOT_ACCEPTABLE = 406;

    public static final int SC_REQUEST_TIMEOUT = 408;

    public static final int SC_CONFLICT = 409;

    public static final int SC_GONE = 410;

    public static final int SC_LENGTH_REQUIRED = 411;

    public static final int SC_PRECONDITION_FAILED = 412;

    public static final int SC_REQUEST_ENTITY_TOO_LARGE = 413;

    public static final int SC_REQUEST_URI_TOO_LONG = 414;

    public static final int SC_UNSUPPORTED_MEDIA_TYPE = 415;

    public static final int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416;

    public static final int SC_EXPECTATION_FAILED = 417;

    public static final int SC_INTERNAL_SERVER_ERROR = 500;

    public static final int SC_NOT_IMPLEMENTED = 501;

    public static final int SC_BAD_GATEWAY = 502;

    public static final int SC_SERVICE_UNAVAILABLE = 503;

    public static final int SC_GATEWAY_TIMEOUT = 504;

    public static final int SC_HTTP_VERSION_NOT_SUPPORTED = 505;

文件下载

package test;

import javax.servlet.ServletException;

import javax.servlet.ServletOutputStream;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.FileInputStream;

import java.io.IOException;

import java.net.URLEncoder;

public class DownServlet extends HttpServlet {

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

this.doPost(req, resp);

    }

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //1.获取下载的文件路径

        String realPath = "D:\\ideaProject\\MavenProject\\ServeltTest\\ContextTest\\src\\main\\resources\\1.png";

        //D:\apache-tomcat-8.5.84\webapps\ContextTest_war\1.png,可以写死，直接写绝对路径

        System.out.println(realPath);

        //2.下载的文件名是什么？

        String substring = realPath.substring(realPath.indexOf("\\") + 1);

        //3.设置想办法让浏览器能够支持下载我们需要的资源

        resp.setHeader("Content-Disposition","attachment;filename"+ URLEncoder.encode(substring,"utf-8"));

        //4.获取下载文件的输入流

        FileInputStream fileInputStream = new FileInputStream(realPath);

        //5.创建缓冲区

        byte[] bytes = new byte[1024];

        int len;

        //6.获取输出流对象

        ServletOutputStream outputStream = resp.getOutputStream();

        //7.文件输出流写入到缓冲区

        while ((len = fileInputStream.read(bytes))!=-1){

            outputStream.write(bytes);

        }

        //8.使用输出流讲缓冲区中的数据输入到客户端

        outputStream.close();

        fileInputStream.close();

    }

}

验证码实现

package test;

import javax.imageio.ImageIO;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.awt.*;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.util.Random;

public class imageServlet extends HttpServlet {

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        this.doGet(req, resp);

    }

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //告诉浏览器每五秒刷新一次

        resp.setHeader("refresh","5");

        //在内存中创建图片

        BufferedImage bufferedImage = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);

        Graphics graphics = bufferedImage.getGraphics();//生成画笔工具

        graphics.setColor(Color.white);//设置画笔颜色白色

        graphics.fillRect(0,0,80,20);//画出一个矩形图片宽80高20再0,0位置

        //生成随机数

        graphics.setColor(Color.BLUE);//设置画笔颜色蓝色

        graphics.setFont(new Font(null,Font.BOLD,20));//设置字体

        graphics.drawString(makeInt(),0,20);//画出String

        resp.setContentType("image/jpeg");//告诉浏览器响应类型

        resp.setDateHeader("expires",-1);//告诉浏览器数据不缓存

        resp.setHeader("Cache-Control","no-cache");//缓存控制，不缓存

        resp.setHeader("Pragma","no-cache");

//使用ImageIO写出image对象

        ImageIO.write(bufferedImage,"jpeg",resp.getOutputStream());

    }

    public String makeInt(){

        Random random = new Random();

        int i = random.nextInt(9999999);

        String s = "" + i;

        StringBuffer buffer = new StringBuffer();

        for (int j = 0;j < 7-s.length();j++){

            int nextInt = random.nextInt(10);

            String s1 = nextInt + "";

            buffer.append(s1);

        }

        s = buffer.toString() + s;

        return s;

    }

}

实现重定向

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        resp.sendRedirect("/ContextTest_war/image");

}//重定向，实现请求转发

等价于

resp.setHeader("Location","/ContextTest_war/image");

        resp.setStatus(302);


<html>

<body>

<h2>Hello World!</h2>

<form action="${pageContext.request.contextPath}/login" method="get">

    <input type="text" name="username"> username

    <input type="password" name="password"> password

<input type="submit">

</form>

</body>

</html>


package test;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

public class LoginServlet extends HttpServlet {

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        this.doGet(req, resp);

    }

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        System.out.println("login");

        resp.setHeader("Location","/ContextTest_war/image");

        resp.setStatus(302);

        System.out.println(req.getParameter("username"));

        System.out.println(req.getParameter("password"));

    }

}

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