但是使用中遇到的第一个问题就是，Extjs那庞大的个头。想办法压缩ExtJS的大小成了首先要解决的问题。
谈谈我的解决方法。
1、压缩混淆
除了ExtJS的大个子以外，引用的很多其他的js库，项目中自己的js文件等等。采用OPOA组件式开发最后一定会增大js文件的总量。所以项目后期要对这些文件进行压缩合并。现在流行的js压缩工具有很多，如packer,jsMin,Esc,JSA,yui-compressor等等。经过实际使用我选的是yui-compressor.
yui-compressor项目地址：http://developer.yahoo.com/yui/compressor/
下载后得到一个java开发的jar包。使用方法基于命令行:
java -jar yuicompressor-x.y.z.jar [options] [input file]
开发中的js文件不可能一个个的手动压缩，这里用到了ANT。在项目构建中可以替你完成以上任务。
Java代码
2、gzip压缩。
坛子里讨论的gzip压缩有2种，
一是有的容器（服务器）提供的功能，但这个局限于特定容器。比如apache+tomcat或者resin-pro版。
二是部署前手动gzip压缩，配合servlet过滤器使用，这个能实现gzip功能，但是降低了灵活性。
我自己用的是自己的实现，采用gzip servlet filter实现。下面是我的代码参考网上内容.
Java代码
package sh.blog.util.web.filter;
import java.io.IOException;
import java.util.zip.GZIPOutputStream;
import javax.servlet.ServletOutputStream;
public class CompressedStream extends ServletOutputStream {
private ServletOutputStream out;
private GZIPOutputStream gzip;
/**
* 指定压缩缓冲流
* @param 输出流到压缩
* @throws IOException if an error occurs with the {@link GZIPOutputStream}.
*/
public CompressedStream(ServletOutputStream out) throws IOException {
this.out = out;
reset();
}
/** @see ServletOutputStream * */
public void close() throws IOException {
gzip.close();
}
/** @see ServletOutputStream * */
public void flush() throws IOException {
gzip.flush();
}
/** @see ServletOutputStream * */
public void write(byte[] b) throws IOException {
write(b, 0, b.length);
}
/** @see ServletOutputStream * */
public void write(byte[] b, int off, int len) throws IOException {
gzip.write(b, off, len);
}
/** @see ServletOutputStream * */
public void write(int b) throws IOException {
gzip.write(b);
}
/**
* Resets the stream.
*
* @throws IOException if an I/O error occurs.
*/
public void reset() throws IOException {
gzip = new GZIPOutputStream(out);
}
}
Java代码
package sh.blog.util.web.filter;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
public class CompressionResponse extends HttpServletResponseWrapper {
protected HttpServletResponse response;
private ServletOutputStream out;
private CompressedStream compressedOut;
private PrintWriter writer;
protected int contentLength;
/**
* 创建一个新的被压缩响应给HTTP
*
* @param response the HTTP response to wrap.
* @throws IOException if an I/O error occurs.
*/
public CompressionResponse(HttpServletResponse response) throws IOException {
super(response);
this.response = response;
compressedOut = new CompressedStream(response.getOutputStream());
}
/**
* Ignore attempts to set the content length since the actual content length
* will be determined by the GZIP compression.
*
* @param len the content length
*/
public void setContentLength(int len) {
contentLength = len;
}
/** @see HttpServletResponse * */
public ServletOutputStream getOutputStream() throws IOException {
if (null == out) {
if (null != writer) {
throw new IllegalStateException("getWriter() has already been called on this response.");
}
out = compressedOut;
}
return out;
}
/** @see HttpServletResponse * */
public PrintWriter getWriter() throws IOException {
if (null == writer) {
if (null != out) {
throw new IllegalStateException("getOutputStream() has already been called on this response.");
}
writer = new PrintWriter(compressedOut);
}
return writer;
}
/** @see HttpServletResponse * */
public void flushBuffer() {
try {
if (writer != null) {
writer.flush();
} else if (out != null) {
out.flush();
}
} catch (IOException e) {
e.printStackTrace();
}
}
/** @see HttpServletResponse * */
public void reset() {
super.reset();
try {
compressedOut.reset();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
/** @see HttpServletResponse * */
public void resetBuffer() {
super.resetBuffer();
try {
compressedOut.reset();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
/**
* Finishes writing the compressed data to the output stream. Note: this
* closes the underlying output stream.
*
* @throws IOException if an I/O error occurs.
*/
public void close() throws IOException {
compressedOut.close();
}
}
Java代码
/**
* 如果浏览器支持解压缩,则压缩该代码
* @throws IOException ServletException if an error occurs with the {@link GZIPOutputStream}.
* 如果需要开启该过滤器,在web.xml中加入此代码
*/
package sh.blog.util.web.filter;
import java.io.IOException;
import java.util.Enumeration;
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;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
public class CompressionFilter implements Filter {
protected Log log = LogFactory.getFactory().getInstance(this.getClass().getName());
@SuppressWarnings("unchecked")
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
boolean compress = false;
if (request instanceof HttpServletRequest){
HttpServletRequest httpRequest = (HttpServletRequest) request;
Enumeration headers = httpRequest.getHeaders("Accept-Encoding");
while (headers.hasMoreElements()){
String value = (String) headers.nextElement();
if (value.indexOf("gzip") != -1){
compress = true;
}
}
}
if (compress){//如果浏览器支持则压缩
HttpServletResponse httpResponse = (HttpServletResponse) response;
httpResponse.addHeader("Content-Encoding", "gzip");
CompressionResponse compressionResponse= new CompressionResponse(httpResponse);
chain.doFilter(request, compressionResponse);
compressionResponse.close();
}
else{//如果浏览器不支持则不压缩
chain.doFilter(request, response);
}
}
public void init(FilterConfig config) throws ServletException {
}
public void destroy(){
}
} 下载本文
