??????? 如果浏览器支持 gzip 压缩格式的数据，则将响应的数据使用 gzip 压缩后再输出。
??????? 在 java web 项目的 web.xml 文件中添加如下代码。
monospace !important; font-size: 12px !important; font-style: normal !important; font-weight: normal !important; vertical-align: baseline !important; float: none !important; white-space: pre-wrap;" class="xml comments"><!--压缩过滤器的配置? 开始 -->
?<filter>
?<filter-name>CompressionFilter</filter-name>
?<filter-class>com.hmw.filter.CompressionFilter</filter-class>
?</filter>
??
?<filter-mapping>
?<filter-name>CompressionFilter</filter-name>
???<servlet-name>/LongServlet</servlet-name>
?</filter-mapping>
<!--压缩过滤器的配置? 结束 -->
package?com.hmw.filter;
?
import?java.io.ByteArrayOutputStream;
import?java.io.IOException;
import?java.io.OutputStream;
import?java.io.OutputStreamWriter;
import?java.util.zip.GZIPOutputStream;
?
import?javax.servlet.Filter;
import?javax.servlet.FilterChain;
import?javax.servlet.FilterConfig;
import?javax.servlet.ServletException;
import?javax.servlet.ServletRequest;
import?javax.servlet.ServletResponse;
import?javax.servlet.http.HttpServletRequest;
import?javax.servlet.http.HttpServletResponse;
?
/**
?* 压缩过滤器 <br>
?* 如果浏览器支持 gzip 压缩格式的数据，则将响应的数据使用 gzip 压缩后再输出。
?*/
public?class?CompressionFilter implements?Filter {
?
????@Override
????public?void?init(FilterConfig config) throws?ServletException {
????}
?
????/**
?????* 如果浏览器不支持 gzip 压缩，则不做直接放行（不做压缩处理）<br>
?????* 反之，将HTTP响应头的编码设置为 <code>gzip</code>，然后将响应数据使用 gzip 进行压缩处理。
?????*/
????@Override
????public?void?doFilter(ServletRequest request, ServletResponse response,
????????????FilterChain chain) throws?ServletException, IOException {
????????HttpServletRequest req = (HttpServletRequest) request;
????????HttpServletResponse res = (HttpServletResponse) response;
?
????????if?(!isGzipSupported(req)) { // Invoke resource normally.
????????????chain.doFilter(req, res);
????????????return;
????????}
?
????????// 将响应头信息中的内容编码设置为 gzip
????????res.setHeader("Content-Encoding", "gzip");
?????????
????????// 调用资源，使用 CharArrayWrapper 包装输出
????????CharArrayWrapper responseWrapper = new?CharArrayWrapper(res);
????????chain.doFilter(req, responseWrapper);
????????// 取得存放输出数据的 char 型数组
????????char[] responseChars = responseWrapper.toCharArray();
?????????
????????// 将响应数据压缩后存入一个 byte 型的数组，然后输出到
????????ByteArrayOutputStream byteStream = new?ByteArrayOutputStream();
????????GZIPOutputStream zipOut = new?GZIPOutputStream(byteStream);
????????OutputStreamWriter tempOut = new?OutputStreamWriter(zipOut);
????????// 将原来的响应数据压缩后写入二字节输出流
????????tempOut.write(responseChars);
????????// 关闭输出流
????????tempOut.close();
?
????????// 更新响应头信息中 Content-Length 的值。
????????res.setContentLength(byteStream.size());
????????// 将压缩后的数据发送至客户端
????????OutputStream realOut = res.getOutputStream();
????????byteStream.writeTo(realOut);
????}
?
????@Override
????public?void?destroy() {
????}
?
????/**
?????* 检测浏览器是否支持 Gzip 压缩
?????*
?????* @param req HTTP 请求对象
?????* @return 如果浏览器支持 Gzip 压缩，则返回 true，反之，则返回 false
?????*/
????private?boolean?isGzipSupported(HttpServletRequest req) {
????????String browserEncodings = req.getHeader("Accept-Encoding");
????????return?((browserEncodings != null) && (browserEncodings.indexOf("gzip") != -1));
????}
}
package?com.hmw.filter;
?
import?java.io.CharArrayWriter;
import?java.io.PrintWriter;
?
import?javax.servlet.http.HttpServletResponse;
import?javax.servlet.http.HttpServletResponseWrapper;
?
/**
?* A response wrapper that takes everything the client would normally output and
?* saves it in one big character array.
?*/
public?class?CharArrayWrapper extends?HttpServletResponseWrapper {
????private?CharArrayWriter charWriter;
?
????/**
?????* Initializes wrapper.
?????* <P>
?????* First, this constructor calls the parent constructor. That call is
?????* crucial so that the response is stored and thus setHeader, *setStatus,
?????* addCookie, and so forth work normally.
?????* <P>
?????* Second, this constructor creates a CharArrayWriter that will be used to
?????* accumulate the response.
?????*/
????public?CharArrayWrapper(HttpServletResponse response) {
????????super(response);
????????charWriter = new?CharArrayWriter();
????}
?
????/**
?????* When servlets or JSP pages ask for the Writer, don't give them the real
?????* one. Instead, give them a version that writes into the character array.
?????* The filter needs to send the contents of the array to the client (perhaps
?????* after modifying it).
?????*/
????@Override
????public?PrintWriter getWriter() {
????????return?new?PrintWriter(charWriter);
????}
?
????/**
?????* Get a String representation of the entire buffer.
?????* <P>
?????* Be sure <B>not</B> to call this method multiple times on the same
?????* wrapper. The API for CharArrayWriter does not guarantee that it
?????* "remembers" the previous value, so the call is likely to make a new
?????* String every time.
?????*/
????@Override
????public?String toString() {
????????return?charWriter.toString();
????}
?
????/** Get the underlying character array. */
????public?char[] toCharArray() {
????????return?charWriter.toCharArray();
????}
}
?
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