JAVA 非常实用的servlet工具类

import java.io.UnsupportedEncodingException;
import java.util.Enumeration;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.TreeMap;

import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
* Http与Servlet工具类.
*/
public abstract class ServletUtils {

//-- Content Type 定义 --//
public static final String EXCEL_TYPE = "application/vnd.ms-excel";
public static final String HTML_TYPE = "text/html";
public static final String JS_TYPE = "text/javascript";
public static final String JSON_TYPE = "application/json";
public static final String XML_TYPE = "text/xml";
public static final String TEXT_TYPE = "text/plain";

//-- Header 定义 --//
public static final String AUTHENTICATION_HEADER = "Authorization";

//-- 常用数值定义 --//
public static final long ONE_YEAR_SECONDS = 60 * 60 * 24 * 365;

/**
* 设置客户端缓存过期时间 的Header.
*/
public static void setExpiresHeader(HttpServletResponse response, long expiresSeconds) {
//Http 1.0 header
response.setDateHeader("Expires", System.currentTimeMillis() + expiresSeconds * 1000);
//Http 1.1 header
response.setHeader("Cache-Control", "private, max-age=" + expiresSeconds);
}

/**
* 设置禁止客户端缓存的Header.
*/
public static void setDisableCacheHeader(HttpServletResponse response) {
//Http 1.0 header
response.setDateHeader("Expires", 1L);
response.addHeader("Pragma", "no-cache");
//Http 1.1 header
response.setHeader("Cache-Control", "no-cache, no-store, max-age=0");
}

/**
* 设置LastModified Header.
*/
public static void setLastModifiedHeader(HttpServletResponse response, long lastModifiedDate) {
response.setDateHeader("Last-Modified", lastModifiedDate);
}

/**
* 设置Etag Header.
*/
public static void setEtag(HttpServletResponse response, String etag) {
response.setHeader("ETag", etag);
}

/**
* 根据浏览器If-Modified-Since Header, 计算文件是否已被修改.
*
* 如果无修改, checkIfModify返回false ,设置304 not modify status.
*
* @param lastModified 内容的最后修改时间.
*/
public static boolean checkIfModifiedSince(HttpServletRequest request, HttpServletResponse response,
long lastModified) {
long ifModifiedSince = request.getDateHeader("If-Modified-Since");
if ((ifModifiedSince != -1) && (lastModified < ifModifiedSince + 1000)) {
response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
return false;
}
return true;
}

/**
* 根据浏览器 If-None-Match Header, 计算Etag是否已无效.
*
* 如果Etag有效, checkIfNoneMatch返回false, 设置304 not modify status.
*
* @param etag 内容的ETag.
*/
public static boolean checkIfNoneMatchEtag(HttpServletRequest request, HttpServletResponse response, String etag) {
String headerValue = request.getHeader("If-None-Match");
if (headerValue != null) {
boolean conditionSatisfied = false;
if (!"*".equals(headerValue)) {
StringTokenizer commaTokenizer = new StringTokenizer(headerValue, ",");

while (!conditionSatisfied && commaTokenizer.hasMoreTokens()) {
String currentToken = commaTokenizer.nextToken();
if (currentToken.trim().equals(etag)) {
conditionSatisfied = true;
}
}
} else {
conditionSatisfied = true;
}

if (conditionSatisfied) {
response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
response.setHeader("ETag", etag);
return false;
}
}
return true;
}

/**
* 设置让浏览器弹出下载对话框的Header.
*
* @param fileName 下载后的文件名.
*/
public static void setFileDownloadHeader(HttpServletResponse response, String fileName) {
try {
//中文文件名支持
String encodedfileName = new String(fileName.getBytes(), "ISO8859-1");
response.setHeader("Content-Disposition", "attachment; filename=\"" + encodedfileName + "\"");
} catch (UnsupportedEncodingException e) {
}
}

/**
* 取得带相同前缀的Request Parameters.
* 返回的结果的Parameter名已去除前缀.
*/
public static Map<String, Object> getParametersStartingWith(ServletRequest request, String prefix) {
AssertUtils.notNull(request, "Request must not be null");
Enumeration paramNames = request.getParameterNames();
Map<String, Object> params = new TreeMap<String, Object>();
if (prefix == null) {
prefix = "";
}
while (paramNames != null && paramNames.hasMoreElements()) {
String paramName = (String) paramNames.nextElement();
if ("".equals(prefix) || paramName.startsWith(prefix)) {
String unprefixed = paramName.substring(prefix.length());
String[] values = request.getParameterValues(paramName);
if (values == null || values.length == 0) {
// Do nothing, no values found at all.
} else if (values.length > 1) {
params.put(unprefixed, values);
} else {
params.put(unprefixed, values[0]);
}
}
}
return params;
}

/**
* 对Http Basic验证的 Header进行编码.
*/
public static String encodeHttpBasic(String userName, String password) {
String encode = userName + ":" + password;
return "Basic " + EncodeUtils.base64Encode(encode.getBytes());
}
}