Java Web整合开发(3) -- Servlet

时间：2023-03-08 20:39:47

Servlert基本程序架构： (FirstServlet.java + web.xml)

FirstServlet.java

package com.helloben.servlet;

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 FirstServlet extends HttpServlet {

    @Override

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        execute(request, response);

    }

    @Override

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        execute(request, response);

    }

    @Override

    public String getServletInfo() {

        return "Short description";

    }

     protected void execute(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

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

        response.setCharacterEncoding("UTF-8");

        request.setCharacterEncoding("UTF-8");

        String requestUri = request.getRequestURI();

        String method = request.getMethod();

        String param = request.getParameter("param");

        try (PrintWriter out = response.getWriter()) {

            out.println("<!DOCTYPE html>");

            out.println("<html>");

            out.println("<head>");

            out.println("<title>Servlet FirstServlet</title>");

            out.println("</head>");

            out.println("<body>");

            out.println("<h1>FirstServlet at " + request.getContextPath() + "</h1>");

            out.println("以 " + method + " 方式访问该页面。取到的 param 参数为：" + param + "<br/><br/>");

            out.println("<form action='" + requestUri + "' method='get'><input type='text' name='param' value=''><input type='submit' value='以 GET 方式访问 RequestServlet'></form>");

            out.println("<br/><br/>");

            out.println("<form action='" + requestUri + "' method='post'><input type='text' name='param' value=''><input type='submit' value='以 POST 方式访问 RequestServlet'></form>");

            out.println("<br/><br/>");

            out.println("<script>document.write('本页面最后更新时间：' + document.lastModified + '<br /><br/>'); </script>");

            out.println("<script>document.write('本页面URL：' + location + '<br/>' ); </script>");

            out.println("</body>");

            out.println("</html>");

        }

    }

}

web.xml

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

<web-app version="3.0" 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_3_0.xsd">

    <servlet>

        <servlet-name>FirstServlet</servlet-name>

        <servlet-class>com.helloben.servlet.FirstServlet</servlet-class>

    </servlet>

    <servlet-mapping>

        <servlet-name>FirstServlet</servlet-name>

        <url-pattern>/FirstServlet</url-pattern>

    </servlet-mapping>

    <session-config>

        <session-timeout>

            30

        </session-timeout>

    </session-config>

</web-app>

访问路径： http://localhost:8080/ch03servlet/FirstServlet

1. 获取request变量

        String authType = request.getAuthType();

        String localAddr = request.getLocalAddr();

        Locale locale = request.getLocale();

        String localName = request.getLocalName();

        String contextPath = request.getContextPath();

        int localPort = request.getLocalPort();

        String method = request.getMethod();

        String pathInfo = request.getPathInfo();

        String pathTranslated = request.getPathTranslated();

        String protocol = request.getProtocol();

        String queryString = request.getQueryString();

        String remoteAddr = request.getRemoteAddr();

        int port = request.getRemotePort();

        String remoteUser = request.getRemoteUser();

        String requestedSessionId = request.getRequestedSessionId();

        String requestURI = request.getRequestURI();

        StringBuffer requestURL = request.getRequestURL();

        String scheme = request.getScheme();

        String serverName = request.getServerName();

        int serverPort = request.getServerPort();

        String servletPath = request.getServletPath();

        Principal userPrincipal = request.getUserPrincipal();

        String accept = request.getHeader("accept");

        String referer = request.getHeader("referer");

        String userAgent = request.getHeader("user-agent");

        String serverInfo = this.getServletContext().getServerInfo();

2.生成图片验证码(IdentityServlet.java)

package com.helloben.servlet;

import com.sun.image.codec.jpeg.JPEGCodec;

import com.sun.image.codec.jpeg.JPEGImageEncoder;

import java.awt.*;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.util.Random;

import javax.servlet.*;

import javax.servlet.http.*;

public class IdentityServlet extends HttpServlet {

    public static final char[] CHARS = { '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F',

        'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };

    public static Random random = new Random();

    public static String getRandomString() {

        StringBuffer buffer = new StringBuffer();

        for (int i = 0; i < 6; i++) {

            buffer.append(CHARS[random.nextInt(CHARS.length)]);

        }

        return buffer.toString();

    }

    public static Color getRandomColor() {

        return new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255));

    }

    public static Color getReverseColor(Color c) {

        return new Color(255 - c.getRed(), 255 - c.getGreen(), 255 - c.getBlue());

    }

    protected void execute(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("image/jpeg");

        String randomString = getRandomString();

        request.getSession(true).setAttribute("randomString", randomString);

        int width = 100;

        int height = 30;

        Color color = getRandomColor();

        Color reverse = getReverseColor(color);

        BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        Graphics2D g = bufferedImage.createGraphics();

        g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16));

        g.setColor(color);

        g.fillRect(0, 0, width, height);

        g.setColor(reverse);

        g.drawString(randomString, 18, 20);

        for (int i = 0, n = random.nextInt(100); i < n; i++) {

                g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);

        }

        // 转成JPEG格式

        ServletOutputStream out = response.getOutputStream();

        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);

        encoder.encode(bufferedImage);

        out.flush();

    }

}

3. 获取初始化变量

Enumeration params = this.getInitParameterNames();

while(params.hasMoreElements()){

    String usernameParam = (String)params.nextElement();

    String passnameParam = this.getInitParameter(usernameParam);

}

4. 获取上下文变量

ServletContext servletContext = this.getServletConfig().getServletContext();

String uploadFolder = servletContext.getInitParameter("upload folder");

String allowedFileType = servletContext.getInitParameter("allowed file type");

5. 资源注入(InjectionServlet.java)

@Resource(name="hello")

private String hello;

@Resource(name="i")

private int i;

@Resource(name="persons")

private String persons;

web.xml

<env-entry>

    <env-entry-name>persons</env-entry-name>

    <env-entry-type>java.lang.String</env-entry-type>

    <env-entry-value>HelloBen, Tony, Rose, Alix</env-entry-value>

</env-entry>

6. 使用JNDI获取资源

Context ctx = new InitialContext();

String hello = (String)ctx.lookup("hello");

Integer i = (Integer)ctx.lookup("i");

String persons = (String)ctx.lookup("person");

7. 注射数据源

@Resource

javax.sql.DataSource datasource;

public Connection getConnection() throws SQLException{

    Connection conn = datasource.getConnection();

    return conn;

}

8. GET方式提交表单(search.jsp)

<form action='SearchServlet' method='get'>

    <input type="radio" name="type" value="web" checked/>网页

    <input type="text" name="word" value="" style="width:300px; "/>

    <input type="submit" value="用雅虎搜索" style="width:100px; "/>

</form>

URL: http://server:8080/webapp/SearchServlet?type=web&word=wbsn

SearchServlet.java

String word = request.getParameter("word");

String type = request.getParameter("type");

9. POST方式提交表单(postPersonInfo.jsp)

<form action="PostServlet" method="POST">

    <input type="text" name="name" class="text" />

    <input type="password" name="password" class="text" />

</form>

PostServlet.java

String name = request.getParameter("name");

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

String sex = request.getParameter("sex");

int age = 0;

try {

    age = Integer.parseInt(request.getParameter("age"));

}

catch (Exception e) {

}

Date birthday = null;

try {

    DateFormat format = new SimpleDateFormat("yyyy-MM-dd");

    birthday = format.parse(request.getParameter("birthday"));

}

catch (Exception e) {

}

String[] interesting = request.getParameterValues("interesting");

String area = request.getParameter("area");

String description = request.getParameter("description");

String btn = request.getParameter("btn");

10. 上传文件

Web文件上传也采用POST方式。(upload.jsp)

<form action="UploadServlet" method="post" enctype="multipart/form-data">

    <input type="file" name="file1" class="text">

</form>

上传文件时，浏览器以二进制方式发送数据。解析二进制数据需要类库，如SmartUpload与Apache Commons Fileupload。SmatUpload是商业类库，解析过程中数据存放在内存中，因此比较快，但是大文件时会内存溢出。

UploadServlet.java

File file1 = null;

File file2 = null;

String description1 = null;

String description2 = null;

// 使用 DiskFileUpload 对象解析 request

DiskFileUpload diskFileUpload = new DiskFileUpload();

try {

    // 将 解析的结果 放置在 List 中

    List<FileItem> list = diskFileUpload.parseRequest(request);

    out.println("遍历所有的 FileItem ... <br/>");

    // 遍历 list 中所有的 FileItem

    for(FileItem fileItem : list){

        if(fileItem.isFormField()){

            // 如果是 文本域

            if("description1".equals(fileItem.getFieldName())){

                // 如果该 FileItem 名称为 description1

                out.println("遍历到 description1 ... <br/>");

                description1 = new String(fileItem.getString().getBytes(), "UTF-8");

            }

            if("description2".equals(fileItem.getFieldName())){

                // 如果该 FileItem 名称为 description2

                out.println("遍历到 description2 ... <br/>");

                description2 = new String(fileItem.getString().getBytes(), "UTF-8");

            }

        }

        else{

            // 否则，为文件域

            if("file1".equals(fileItem.getFieldName())){

                // 客户端文件路径构建的 File 对象

                File remoteFile = new File(new String(fileItem.getName().getBytes(), "UTF-8"));

                out.println("遍历到 file1 ... <br/>");

                out.println("客户端文件位置: " + remoteFile.getAbsolutePath() + "<br/>");

                // 服务器端文件，放在 upload 文件夹下

                file1 = new File(this.getServletContext().getRealPath("attachment"), remoteFile.getName());

                file1.getParentFile().mkdirs();

                file1.createNewFile();

                // 写文件，将 FileItem 的文件内容写到文件中

                InputStream ins = fileItem.getInputStream();

                OutputStream ous = new FileOutputStream(file1);

                try{

                    byte[] buffer = new byte[1024];

                    int len = 0;

                    while((len=ins.read(buffer)) > -1) {

                        ous.write(buffer, 0, len);

                    }

                    out.println("已保存文件" + file1.getAbsolutePath() + "<br/>");

                }

                finally{

                    ous.close();

                    ins.close();

                }

            }

            if("file2".equals(fileItem.getFieldName())){

                // 客户端文件路径构建的 File 对象

                File remoteFile = new File(new String(fileItem.getName().getBytes(), "UTF-8"));

                out.println("遍历到 file2 ... <br/>");

                out.println("客户端文件位置: " + remoteFile.getAbsolutePath() + "<br/>");

                // 服务器端文件，放在 upload 文件夹下

                file2 = new File(this.getServletContext().getRealPath("attachment"), remoteFile.getName());

                file2.getParentFile().mkdirs();

                file2.createNewFile();

                // 写文件，将 FileItem 的文件内容写到文件中

                InputStream ins = fileItem.getInputStream();

                OutputStream ous = new FileOutputStream(file2);

                try{

                    byte[] buffer = new byte[1024];

                    int len = 0;

                    while((len=ins.read(buffer)) > -1) {

                        ous.write(buffer, 0, len);

                    }

                    out.println("已保存文件" + file2.getAbsolutePath() + "<br/>");

                }

                finally{

                    ous.close();

                    ins.close();

                }

            }

        }

    }

    out.println("Request 解析完毕");

}

catch (FileUploadException e) {

    // TODO Auto-generated catch block

    e.printStackTrace();

}

11. 带进度条的文件上传

实时显示上传进度的原理是服务器在处理上传文件的同事，将上传进度的信息如文件总长度、已上传多少，传输速率等写入Session中。客户端浏览器利用Ajax技术再新开一个独立的线程从Session中获取上传进度信息，并实时显示。Session可以看做是服务器内存。

uploadprogress.jsp

<%@page language="java" contentType="text/html" pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

    <head>

        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

        <title>上传文件</title>

        <style type="text/css">

            body, td, div {

                font-size: 12px;

                font-familly: 宋体;

            }

            #progressBar {

                width: 400px;

                height: 12px;

                background: #FFFFFF;

                border: 1px solid #000000;

                padding: 1px;

            }

            #progressBarItem {

                width: 30%;

                height: 100%;

                background: #FF0000;

            }

        </style>

        <script type="text/javascript">

            var _finished = true;

            function $(obj){

                return document.getElementById(obj);

            }

            function showStatus(){

                _finished = false;

                $('status').style.display = 'block';

                $('progressBarItem').style.width = '1%';

                $('btnSubmit').disabled = true;

                setTimeout("requestStatus()", 1000);

            }

            function requestStatus(){

                if(_finished) {

                    return;

                }

                var req = createRequest(); 

                req.open("GET", "ProgressUploadServlet");

                req.onreadystatechange = function(){

                    callback(req);

                }

                req.send(null);

                setTimeout("requestStatus()", 1000);

            }

            function createRequest()

            {

                if(window.XMLHttpRequest)//ns

                {

                    return new XMLHttpRequest();

                }

                else//IE

                {

                    try{

                        return new ActiveXObject("Msxml2.XMLHTTP");

                    }

                    catch(e){

                        return new ActiveXObject("Microsoft.XMLHTTP");

                    }

                }

                return null;

            }

            function callback(req){

                if(req.readyState == 4) {

                    if(req.status != 200){

                        _debug("发生错误。 req.status: " + req.status + "");

                        return;

                    }

                    _debug("status.jsp 返回值：" + req.responseText);

                    var ss = req.responseText.split("||");

                    // 格式：百分比||已完成数(M)||文件总长度(M)||传输速率(K)||已用时间(s)||估计总时间(s)||估计剩余时间(s)||正在上传第几个文件

                    $('progressBarItem').style.width = '' + ss[0] + '%';

                    $('statusInfo').innerHTML = '已完成百分比: ' + ss[0] + '% <br />已完成数(M): ' + ss[1] + '<br/>文件总长度(M): ' + ss[2] + '<br/>传输速率(K): ' + ss[3] + '<br/>已用时间(s): ' + ss[4] + '<br/>估计总时间(s): ' + ss[5] + '<br/>估计剩余时间(s): ' + ss[6] + '<br/>正在上传第几个文件: ' + ss[7];

                    if(ss[1] == ss[2]){

                        _finished = true;

                        $('statusInfo').innerHTML += "<br/><br/><br/>上传已完成。";

                        $('btnSubmit').disabled = false;

                    }

                }

            }

            function _debug(obj){

                var div = document.createElement("DIV");

                div.innerHTML = "[debug]: " + obj;

                document.body.appendChild(div);

            }

        </script>

    </head>

    <body>

        <iframe name=upload_iframe width=0 height=0></iframe>

        <form action="ProgressUploadServlet" method="post" enctype="multipart/form-data" target="upload_iframe" onsubmit="showStatus()">

            <input type="file" name="file1" style="width: 350px; "> <br />

            <input type="file" name="file2" style="width: 350px; "> <br />

            <input type="file" name="file3" style="width: 350px; "> <br />

            <input type="file" name="file4" style="width: 350px; ">

            <input type="submit" value=" 开始上传 " id="btnSubmit"></form>

            <div id="status" style="display: none; ">

                    上传进度条：

                    <div id="progressBar">

                        <div id="progressBarItem"></div>

                    </div>

                    <div id="statusInfo"></div>

            </div>

        </form>

    </body>

</html>

ProgressUploadServlet.java

package com.helloben.servlet.upload;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.io.PrintWriter;

import java.util.Iterator;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;

import org.apache.commons.fileupload.disk.DiskFileItemFactory;

import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class ProgressUploadServlet extends HttpServlet {

    @Override

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setHeader("Cache-Control", "no-store");

        response.setHeader("Pragrma", "no-cache");

        response.setDateHeader("Expires", 0);

        UploadStatus status = (UploadStatus) request.getSession(true).getAttribute("uploadStatus");

        if (status == null) {

            response.getWriter().println("没有上传信息");

            return;

        }

        long startTime = status.getStartTime();

        long currentTime = System.currentTimeMillis();

        long time = (currentTime - startTime) / 1000 + 1;

        double velocity = ((double) status.getBytesRead()) / (double) time;

        double totalTime = status.getContentLength() / velocity;

        double timeLeft = totalTime - time;

        int percent = (int) (100 * (double) status.getBytesRead() / (double) status.getContentLength());

        double length = ((double) status.getBytesRead()) / 1024 / 1024;

        double totalLength = ((double) status.getContentLength()) / 1024 / 1024;

        // 格式：百分比||已完成数(M)||文件总长度(M)||传输速率(K)||已用时间(s)||估计总时间(s)||估计剩余时间(s)||正在上传第几个文件

        String value = percent + "||" + length + "||" + totalLength + "||"

            + velocity + "||" + time + "||" + totalTime + "||" + timeLeft + "||" + status.getItems();

        response.getWriter().println(value);

    }

    @Override

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        UploadStatus status = new UploadStatus();

        UploadListener listener = new UploadListener(status);

        request.getSession(true).setAttribute("uploadStatus", status);

        // Apache 上传工具

        ServletFileUpload upload = new ServletFileUpload(new DiskFileItemFactory());

        upload.setProgressListener(listener);

        try {

            List itemList = upload.parseRequest(request);

            for (Iterator it = itemList.iterator(); it.hasNext();) {

                FileItem item = (FileItem) it.next();

                if (item.isFormField()) {

                    System.out.println("FormField: " + item.getFieldName() + " = " + item.getString());

                }

                else {

                    System.out.println("File: " + item.getName());

                    // 统一 Linux 与 windows 的路径分隔符

                    String fileName = item.getName().replace("/", "\\");

                    fileName = fileName.substring(fileName.lastIndexOf("\\"));

                    File saved = new File("C:\\upload_test", fileName);

                    saved.getParentFile().mkdirs();

                    InputStream ins = item.getInputStream();

                    OutputStream ous = new FileOutputStream(saved);

                    byte[] tmp = new byte[1024];

                    int len = -1;

                    while ((len = ins.read(tmp)) != -1) {

                            ous.write(tmp, 0, len);

                    }

                    ous.close();

                    ins.close();

                    response.getWriter().println("已保存文件：" + saved);

                }

            }

        }

        catch (Exception e) {

            e.printStackTrace();

            response.getWriter().println("上传发生错误：" + e.getMessage());

        }

    }

    @Override

    public String getServletInfo() {

        return "Short description";

    }

}

UploadListener.java

package com.helloben.servlet.upload;

import org.apache.commons.fileupload.ProgressListener;

public class UploadListener implements ProgressListener {

    private UploadStatus status;

    public UploadListener(UploadStatus status) {

        this.status = status;

    }

    @Override

    public void update(long bytesRead, long contentLength, int items) {

        status.setBytesRead(bytesRead);

        status.setContentLength(contentLength);

        status.setItems(items);

    }

}

UploadStatus.java

package com.helloben.servlet.upload;

class UploadStatus {

    private long bytesRead;

    private long contentLength;

    private int items;

    private long startTime = System.currentTimeMillis();

    public long getBytesRead() {

        return bytesRead;

    }

    public void setBytesRead(long bytesRead) {

        this.bytesRead = bytesRead;

    }

    public long getContentLength() {

        return contentLength;

    }

    public void setContentLength(long contentLength) {

        this.contentLength = contentLength;

    }

    public int getItems() {

        return items;

    }

    public void setItems(int items) {

        this.items = items;

    }

    public long getStartTime() {

        return startTime;

    }

    public void setStartTime(long startTime) {

        this.startTime = startTime;

    }

}

12. Servlet生命周期(init() --> service() --> destroy())

13. web.xml文件详解 (http://www.cnblogs.com/hellojava/archive/2012/12/28/2835730.html)

相关文章