/*******************************************************************************
* Copyright (c) 2005, 2014 springside.github.io
*
* Licensed under the Apache License, Version 2.0 (the "License");
*******************************************************************************/
package org.springside.examples.showcase.demos.web;
import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.util.zip.GZIPOutputStream;
import javax.activation.MimetypesFileTypeMap;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.io.FileUtils;
import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.StringUtils;
import org.springframework.context.ApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;
import org.springside.modules.web.Servlets;
/**
* 本地静态内容展示与下载的Servlet.
*
* 演示文件高效读取,客户端缓存控制及Gzip压缩传输.
* 可使用org.springside.examples.showcase.cache包下的Ehcache或本地Map缓存静态内容基本信息(未演示).
*
* 演示访问地址为：
* static-content?contentPath=static/images/logo.jpg
* static-content?contentPath=static/images/logo.jpg&download=true
*
* @author calvin
*/
public class StaticContentServlet extends HttpServlet {
private static final long serialVersionUID = -1855617048198368534L;
/** 需要被Gzip压缩的Mime类型. */
private static final String[] GZIP_MIME_TYPES = { "text/html", "application/xhtml+xml", "text/plain", "text/css",
"text/javascript", "application/x-javascript", "application/json" };
/** 需要被Gzip压缩的最小文件大小. */
private static final int GZIP_MINI_LENGTH = 512;
private MimetypesFileTypeMap mimetypesFileTypeMap;
private ApplicationContext applicationContext;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 取得参数
String contentPath = request.getParameter("contentPath");
if (StringUtils.isBlank(contentPath)) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, "contentPath parameter is required.");
return;
}
// 获取请求内容的基本信息.
ContentInfo contentInfo = getContentInfo(contentPath);
// 根据Etag或ModifiedSince Header判断客户端的缓存文件是否有效, 如仍有效则设置返回码为304,直接返回.
if (!Servlets.checkIfModifiedSince(request, response, contentInfo.lastModified)
|| !Servlets.checkIfNoneMatchEtag(request, response, contentInfo.etag)) {
return;
}
// 设置Etag/过期时间
Servlets.setExpiresHeader(response, Servlets.ONE_YEAR_SECONDS);
Servlets.setLastModifiedHeader(response, contentInfo.lastModified);
Servlets.setEtag(response, contentInfo.etag);
// 设置MIME类型
response.setContentType(contentInfo.mimeType);
// 设置弹出下载文件请求窗口的Header
if (request.getParameter("download") != null) {
Servlets.setFileDownloadHeader(request, response, contentInfo.fileName);
}
// 构造OutputStream
OutputStream output;
if (checkAccetptGzip(request) && contentInfo.needGzip) {
// 使用压缩传输的outputstream, 使用http1.1 trunked编码不设置content-length.
output = buildGzipOutputStream(response);
} else {
// 使用普通outputstream, 设置content-length.
response.setContentLength(contentInfo.length);
output = response.getOutputStream();
}
// 高效读取文件内容并输出,然后关闭input file
FileUtils.copyFile(contentInfo.file, output);
output.flush();
}
/**
* 检查浏览器客户端是否支持gzip编码.
*/
private static boolean checkAccetptGzip(HttpServletRequest request) {
// Http1.1 header
String acceptEncoding = request.getHeader("Accept-Encoding");
return StringUtils.contains(acceptEncoding, "gzip");
}
/**
* 设置Gzip Header并返回GZIPOutputStream.
*/
private OutputStream buildGzipOutputStream(HttpServletResponse response) throws IOException {
response.setHeader("Content-Encoding", "gzip");
response.setHeader("Vary", "Accept-Encoding");
return new GZIPOutputStream(response.getOutputStream());
}
/**
* 初始化.
*/
@Override
public void init() throws ServletException {
// 保存applicationContext以备后用，纯演示.
applicationContext = WebApplicationContextUtils.getWebApplicationContext(getServletContext());
// 初始化mimeTypes, 默认缺少css的定义,添加之.
mimetypesFileTypeMap = new MimetypesFileTypeMap();
mimetypesFileTypeMap.addMimeTypes("text/css css");
}
/**
* 创建Content基本信息.
*/
private ContentInfo getContentInfo(String contentPath) {
ContentInfo contentInfo = new ContentInfo();
String realFilePath = getServletContext().getRealPath(contentPath);
File file = new File(realFilePath);
contentInfo.file = file;
contentInfo.contentPath = contentPath;
contentInfo.fileName = file.getName();
contentInfo.length = (int) file.length();
contentInfo.lastModified = file.lastModified();
contentInfo.etag = "W/\"" + contentInfo.lastModified + "\"";
contentInfo.mimeType = mimetypesFileTypeMap.getContentType(contentInfo.fileName);
if ((contentInfo.length >= GZIP_MINI_LENGTH) && ArrayUtils.contains(GZIP_MIME_TYPES, contentInfo.mimeType)) {
contentInfo.needGzip = true;
} else {
contentInfo.needGzip = false;
}
return contentInfo;
}
/**
* 定义Content的基本信息.
*/
static class ContentInfo {
protected String contentPath;
protected File file;
protected String fileName;
protected int length;
protected String mimeType;
protected long lastModified;
protected String etag;
protected boolean needGzip;
}
}