静态资源的缓存策略
在web服务器部署的时候，我们都会考虑将页面静态化，尤其是首页。这样不但提高访问速度，还有助于爬虫的抓去。一般静态资源有CDN；如果项目没用CDN，还可以用varnish、squid做静态缓存；如果都还没用到，那可以使用apache的mod_cache和nginx的proxy_cache。这篇文章不是描述怎么配置这些服务器缓存静态资源，主要是描述利用一些模版引擎生成静态页面，然后用一些缓存策略将静态资源缓存于nginx或apache，而不用去后端访问tomcat/jetty之类的web容器。
1.先来看一下下面这张图，一个非常简单的部署，nginx这里反向代理，作为负载均衡器，更重要的是静态资源的缓存服务器。这是最近做的一个小项目采取的静态资源的缓存方案。
2.将htm js css png等静态资源全部存在nginx服务器上，因为只是一个简单的项目，所以nginx的缓存完全满足业务要求，再做一层浏览器缓存。
第一次nginx到后端服务器时，如果不存再静态htm，还是将访问动态资源，这个用拦截器实现，后端有个schedule每一小时生成静态页面，本项目使用velocity作为view层模版引擎。
生成静态资源代码：
package com.tcl.mie.appstore.webapp.controller.staticVM;
import java.io.RandomAccessFile;
import java.io.StringWriter;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Files;
import java.nio.file.LinkOption;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Map;
import java.util.Map.Entry;
import javax.servlet.http.HttpServletRequest;
import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.view.velocity.VelocityConfigurer;
import com.tcl.mie.appstore.biz.util.StringUtil;
/**
*
* 创建人: sosop.hou
*
* 创建时间：Apr 1, 2015 2:53:26 PM
*
* @ClassName: VmToHtml
* @Description: vm模板生成html内容，便于静态缓存
*/
@Component
public class VmToHtml {
private final Logger LOG = LoggerFactory.getLogger(VmToHtml.class);
@Autowired
private VelocityConfigurer velocityConfigurer;
public String htmlString(HttpServletRequest request, String vmName,
Map<String, Object> vars) {
Template template =
velocityConfigurer.getVelocityEngine().getTemplate(
StringUtil.append(vmName, ".vm"), "UTF-8");
VelocityContext context = new VelocityContext();
if (null != vars) {
for (Entry<String, Object> var : vars.entrySet()) {
context.put(var.getKey(), var.getValue());
}
}
String contextPath = request.getContextPath();
context.put("basePath", contextPath);
StringWriter sw = new StringWriter();
template.merge(context, sw);
return sw.toString().replaceAll("\\$basePath", contextPath)
.replaceAll("\\$\\{basePath\\}", contextPath);
}
public void htmlFile(HttpServletRequest request, String vmName,
Map<String, Object> vars, String htmlName) {
String html = htmlString(request, vmName, vars);
String storePath =
((String) velocityConfigurer.getVelocityEngine().getProperty(
Velocity.FILE_RESOURCE_LOADER_PATH));
Path path = Paths.get(storePath);
path = path.getParent().getParent().resolve("html").resolve(htmlName);
RandomAccessFile file = null;
FileChannel channel = null;
try {
file = new RandomAccessFile(path.toFile(), "rw");
channel = file.getChannel();
ByteBuffer buf = ByteBuffer.wrap(html.getBytes());
channel.write(buf);
} catch (Exception e) {
LOG.error(e.getMessage(), e);
} finally {
try {
if (channel != null && channel.isOpen()) {
channel.close();
channel = null;
}
if (file != null) {
file.close();
file = null;
}
} catch (Exception e) {
LOG.error(e.getMessage(), e);
}
}
}
public boolean htmlIsExists(String htmlName) {
Path path = getPath(htmlName);
if (Files.exists(path, LinkOption.NOFOLLOW_LINKS)) {
return true;
}
return false;
}
public long getLastModifyTime(String htmlName) {
Path path = getPath(htmlName);
return path.toFile().lastModified();
}
private Path getPath(String htmlName) {
String storePath =
((String) velocityConfigurer.getVelocityEngine().getProperty(
Velocity.FILE_RESOURCE_LOADER_PATH));
Path path =
Paths.get(storePath).getParent().getParent().resolve("html")
.resolve(htmlName);
return path;
}
}
注解代码：
package com.tcl.mie.appstore.webapp.util.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
@Documented
public @interface StaticPage {
long expireMinutes() default 30L;
}
定时任务代码：
package com.tcl.mie.appstore.webapp.job;
import java.io.IOException;
import java.util.Properties;
import org.apache.log4j.Logger;
import com.tcl.mie.appstore.common.config.ConfigUtil;
import com.tcl.mie.appstore.webapp.util.HttpRequestUtil;
/**
*
* 创建人: sosop.hou
*
* 创建时间：Apr 3, 2015 1:58:13 PM
*
* @ClassName: CreateStaticPageJob
* @Description: 定时创建静态页面
*/
public class CreateStaticPageJob {
private final static Logger LOG = Logger
.getLogger(CreateStaticPageJob.class);
public static void createStaticPages() throws IOException {
LOG.info("start create static page.");
Properties props = new Properties();
props.load(CreateStaticPageJob.class
.getResourceAsStream("/staticPage.properties"));
String rootUrl = ConfigUtil.getServerConfig().getString("rootUrl");
String[] filerUris = props.getProperty("filterUris").split(",");
for (String uri : filerUris) {
HttpRequestUtil.get(rootUrl, uri);
}
}
}
拦截器代码：
package com.tcl.mie.appstore.webapp.controller.staticVM;
import java.lang.annotation.Annotation;
import java.util.Date;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import com.tcl.mie.appstore.biz.util.StringUtil;
import com.tcl.mie.appstore.common.config.ConfigUtil;
import com.tcl.mie.appstore.webapp.util.HttpRequestUtil;
import com.tcl.mie.appstore.webapp.util.annotation.StaticPage;
public class VisitStaticInterceptor implements HandlerInterceptor {
@Autowired
private VmToHtml vmToHtml;
private String baseDir = "/web/html";
private Map<String, Long> expired = new HashMap<>();
@Override
public boolean preHandle(HttpServletRequest request,
HttpServletResponse response, Object handler) throws Exception {
String htmlName = generateHtmlName(request);
if (!localRequest(request)
&& isAnnotaition(handler, StaticPage.class)
&& vmToHtml.htmlIsExists(htmlName)
&& notExpire(
request,
htmlName,
(StaticPage) getAnnotationInstance(handler,
StaticPage.class))) {
response.sendRedirect(StringUtil.append(baseDir, "/", htmlName));
return false;
}
return true;
}
@Override
public void postHandle(HttpServletRequest request,
HttpServletResponse response, Object handler,
ModelAndView modelAndView) throws Exception {
String htmlName = generateHtmlName(request);
if (null != modelAndView && localRequest(request)
&& isAnnotaition(handler, StaticPage.class)) {
vmToHtml.htmlFile(request, modelAndView.getViewName(),
modelAndView.getModel(), htmlName);
expired.put(
htmlName,
vmToHtml.getLastModifyTime(htmlName)
+ ((StaticPage) getAnnotationInstance(handler,
StaticPage.class)).expireMinutes() * 60
* 1000);
}
}
@Override
public void afterCompletion(HttpServletRequest request,
HttpServletResponse response, Object handler, Exception ex)
throws Exception {
}
@SuppressWarnings("rawtypes")
private boolean isAnnotaition(Object handler, Class clazz) {
if (!(handler instanceof HandlerMethod)) {
return false;
}
if (getAnnotationInstance(handler, clazz) != null) {
return true;
}
return false;
}
@SuppressWarnings({"unchecked", "rawtypes"})
private Annotation getAnnotationInstance(Object handler, Class clazz) {
return ((HandlerMethod) handler).getMethodAnnotation(clazz);
}
@SuppressWarnings("unchecked")
private String generateHtmlName(HttpServletRequest request) {
String paramsHtm = "_";
Enumeration<String> iterator = request.getParameterNames();
String paramName;
while (iterator.hasMoreElements()) {
paramName = iterator.nextElement();
paramsHtm =
StringUtil.append(paramsHtm, paramName, "_",
request.getParameter(paramName), "_");
}
String requestPath = request.getServletPath().replaceAll("/", "_");
return StringUtil.append(requestPath, paramsHtm, ".htm");
}
private boolean localRequest(HttpServletRequest request) {
String remoteHost = request.getRemoteHost();
if ("0:0:0:0:0:0:0:1".equals(remoteHost.trim())
|| "localhost".equals(remoteHost.trim())
|| "127.0.0.1".equals(remoteHost.trim())) {
return true;
}
return false;
}
@SuppressWarnings("unchecked")
private boolean notExpire(HttpServletRequest request, String htmlName,
StaticPage staticPage) {
long lastModifyTime;
// 判断是否保存过期时间
if (expired.containsKey(htmlName)) {
lastModifyTime = expired.get(htmlName);
} else {
lastModifyTime =
vmToHtml.getLastModifyTime(htmlName)
+ staticPage.expireMinutes() * 60 * 1000;
expired.put(htmlName, lastModifyTime);
}
// 判断是够过期
long now = new Date().getTime();
if (now < lastModifyTime) {
return true;
} else {
Enumeration<String> iterator = request.getParameterNames();
String params = "?";
String paramName;
while (iterator.hasMoreElements()) {
paramName = iterator.nextElement();
params =
StringUtil.append(params, paramName, "=",
request.getParameter(paramName), "&");
}
HttpRequestUtil.get(
ConfigUtil.getServerConfig().getString("rootUrl"),
StringUtil.append(request.getServletPath(), params));
}
return false;
}
}