java servlet对html网页压缩后返回的过滤器代码实现 -

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java servlet对html网页压缩后返回的过滤器代码实现

博客分类：

freemark

freemarker html

最近分享代码较少，正好在优化最代码关于返回的html代码的压缩上有些相关经验分享下。
【参考：http://www.zuidaima.com/share/2633847241772032.htm】
之前研究的是通过freemarker的原生macro实现的：

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<@compress single_line=true>
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<html>
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freemarker template技术
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</html>
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</@compress>
但因为最代码目前已经有几十个template文件，一个个加的话太费时费力了，另外如果不是freemarker技术的话就不能使用这个机制了，感觉java应该有这种技术来实现压缩的功能，于是想到了Filter

HtmlFilter.java

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package com.zuidaima.filter;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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import java.io.PrintWriter;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.regex.Matcher;
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import java.util.regex.Pattern;
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import javax.servlet.Filter;
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import javax.servlet.FilterChain;
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import javax.servlet.FilterConfig;
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import javax.servlet.ServletException;
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import javax.servlet.ServletOutputStream;
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import javax.servlet.ServletRequest;
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import javax.servlet.ServletResponse;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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import javax.servlet.http.HttpServletResponseWrapper;
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/**
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*@author www.zuidaima.com
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**/
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public class HtmlFilter implements Filter {
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    public static final String codePatternStr = "(<|<)p-re[\\w\\W]*?[\\w\\W]*?/p-re[\\w\\W]*?(>|>)";
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    public static final Pattern codePattern = Pattern.compile(codePatternStr,
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            Pattern.CASE_INSENSITIVE);
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    private FilterConfig filterConfig = null;
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    class CodeFragment {
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        private String left;
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        private String fragment;
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        private String right;
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        public CodeFragment(String left, String fragment, String right) {
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            this.left = left;
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            this.fragment = fragment;
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            this.right = right;
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        }
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        public String getLeft() {
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            return left;
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        }
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        public void setLeft(String left) {
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            this.left = left;
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        }
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        public String getFragment() {
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            return fragment;
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        }
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        public void setFragment(String fragment) {
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            this.fragment = fragment;
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        }
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        public String getRight() {
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            return right;
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        }
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        public void setRight(String right) {
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            this.right = right;
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        }
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    }
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    private static class ByteArrayServletStream extends ServletOutputStream {
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        ByteArrayOutputStream baos;
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        ByteArrayServletStream(ByteArrayOutputStream baos) {
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            this.baos = baos;
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        }
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        public void write(int param) throws IOException {
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            baos.write(param);
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        }
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    }
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    private static class ByteArrayPrintWriter {
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        private ByteArrayOutputStream baos = new ByteArrayOutputStream();
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        private PrintWriter pw = new PrintWriter(baos);
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        private ServletOutputStream sos = new ByteArrayServletStream(baos);
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        public PrintWriter getWriter() {
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            return pw;
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        }
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        public ServletOutputStream getStream() {
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            return sos;
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        }
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        byte[] toByteArray() {
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            return baos.toByteArray();
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        }
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    }
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    public class CharResponseWrapper extends HttpServletResponseWrapper {
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        private ByteArrayPrintWriter output;
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        private boolean usingWriter;
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        public CharResponseWrapper(HttpServletResponse response) {
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            super(response);
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            usingWriter = false;
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            output = new ByteArrayPrintWriter();
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        }
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        public byte[] getByteArray() {
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            return output.toByteArray();
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        }
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        @Override
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        public ServletOutputStream getOutputStream() throws IOException {
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            // will error out, if in use
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            if (usingWriter) {
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                super.getOutputStream();
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            }
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            usingWriter = true;
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            return output.getStream();
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        }
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        @Override
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        public PrintWriter getWriter() throws IOException {
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            // will error out, if in use
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            if (usingWriter) {
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                super.getWriter();
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            }
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            usingWriter = true;
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            return output.getWriter();
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        }
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        public String toString() {
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            return output.toString();
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        }
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    }
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    public void doFilter(ServletRequest request, ServletResponse response,
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            FilterChain chain) throws IOException, ServletException {
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        HttpServletRequest _request = (HttpServletRequest) request;
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        if (_request.getRequestURI().indexOf("update") != -1
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                || _request.getRequestURI().indexOf("create") != -1) {
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            chain.doFilter(request, response);
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            return;
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        }
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        CharResponseWrapper wrappedResponse = new CharResponseWrapper(
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                (HttpServletResponse) response);
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        chain.doFilter(request, wrappedResponse);
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        byte[] bytes = wrappedResponse.getByteArray();
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        String contentType = wrappedResponse.getContentType();
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        if (contentType != null && contentType.matches(".*?(html|json).*?")) {
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            String out = new String(bytes);
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            Matcher matcher = codePattern.matcher(out);
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            List<CodeFragment> codeFragments = new ArrayList<CodeFragment>();
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            while (matcher.find()) {
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                String fragment = matcher.group(0);
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                String left = matcher.group(1);
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                String right = matcher.group(2);
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                CodeFragment codeFragment = new CodeFragment(left, fragment,
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                        right);
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                codeFragments.add(codeFragment);
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                // 占位符<pr-e>idx</pr-e>
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                out = out.replace(fragment, left + "p-re" + right
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                        + codeFragments.size() + left + "/p-re" + right);
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            }
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            out = out.replaceAll("[\r\n]", "").replaceAll(">\\s*?<", "><")
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                    .trim();
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            // 还原占位符
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            for (int i = 0; i < codeFragments.size(); i++) {
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                CodeFragment codeFragment = codeFragments.get(i);
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                String fragment = codeFragment.getFragment();
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                String left = codeFragment.getLeft();
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                String right = codeFragment.getRight();
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                out = out.replace(left + "p-re" + right + (i + 1) + left
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                        + "/p-re" + right, fragment);
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            }
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            response.getOutputStream().write(out.getBytes());
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        } else {
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            response.getOutputStream().write(bytes);
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        }
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    }
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    @Override
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    public void init(FilterConfig filterConfig) throws ServletException {
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        this.filterConfig = filterConfig;
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    }
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    @Override
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    public void destroy() {
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        filterConfig = null;
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    }
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}
刚上线的新鲜代码分享，相信对牛牛们会有所帮助吧。

注意：

1.创建和编辑类的操作不做压缩，因为访问量不大

2.<pre></pre>内部的代码不做处理

3.只对content type为html和json做的做处理

压缩前和压缩后的html代码大小对比如下图

java servlet对html网页压缩后返回的过滤器代码实现

压缩前源码

java servlet对html网页压缩后返回的过滤器代码实现

压缩后源码

java servlet对html网页压缩后返回的过滤器代码实现

另外对seo的影响可能不会很大，毕竟没有改变html结构。

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