java爬虫爬取网页内容前，对网页内容的编码格式进行判断的方式

package com.mobivans.encoding;

import info.monitorenter.cpdetector.io.ASCIIDetector;
import info.monitorenter.cpdetector.io.ByteOrderMarkDetector;
import info.monitorenter.cpdetector.io.CodepageDetectorProxy;
import info.monitorenter.cpdetector.io.JChardetFacade;
import info.monitorenter.cpdetector.io.ParsingDetector;
import info.monitorenter.cpdetector.io.UnicodeDetector;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.nio.charset.Charset;
import java.util.List;
import java.util.Map;

import org.apache.commons.io.IOUtils;

public class PageEncoding {
    /**    测试用例
     * @param args
     */
    public static void main(String[] args) {
        
//        String charset = getEncodingByHeader("http://blog.csdn.net/liuzhenwen/article/details/4060922");
//        String charset = getEncodingByMeta("http://blog.csdn.net/liuzhenwen/article/details/4060922");
        String charset = getEncodingByContentStream("http://blog.csdn.net/liuzhenwen/article/details/5930910");
        
        System.out.println(charset);
    }

    /**
     * 从header中获取页面编码
     * @param strUrl
     * @return
     */
    public static String getEncodingByHeader(String strUrl){
        String charset = null;
        try {
            URLConnection urlConn = new URL(strUrl).openConnection();
            // 获取链接的header
            Map<String, List<String>> headerFields = urlConn.getHeaderFields();
            // 判断headers中是否存在Content-Type
            if(headerFields.containsKey("Content-Type")){
                //拿到header 中的 Content-Type ：[text/html; charset=utf-8]
                List<String> attrs = headerFields.get("Content-Type");
                String[] as = attrs.get(0).split(";");
                for (String att : as) {
                    if(att.contains("charset")){
//                        System.out.println(att.split("=")[1]);
                        charset = att.split("=")[1];
                    }
                }
            } 
            return charset;
        } catch (MalformedURLException e) {
            e.printStackTrace();
            return charset;
        } catch (IOException e) {
            e.printStackTrace();
            return charset;
        }
    }
    
    /**
     * 从meta中获取页面编码
     * @param strUrl
     * @return
     */
    public static String getEncodingByMeta(String strUrl){
        String charset = null;
        try {
            URLConnection urlConn = new URL(strUrl).openConnection();
            //避免被拒绝
            urlConn.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36");
            // 将html读取成行,放入list
            List<String> lines = IOUtils.readLines(urlConn.getInputStream());
            for (String line : lines) {
                if(line.contains("http-equiv") && line.contains("charset")){
//                    System.out.println(line);
                    String tmp = line.split(";")[1];
                    charset = tmp.substring(tmp.indexOf("=")+1, tmp.indexOf("\""));
                }else{
                    continue;
                }
            }
            return charset;
        } catch (MalformedURLException e) {
            e.printStackTrace();
            return charset;
        } catch (IOException e) {
            e.printStackTrace();
            return charset;
        }
    }
    
    /**
     * 根据网页内容获取页面编码
     *     case : 适用于可以直接读取网页的情况(例外情况:一些博客网站禁止不带User-Agent信息的访问请求)
     * @param url
     * @return
     */
    public static String getEncodingByContentUrl(String url) {
        CodepageDetectorProxy cdp = CodepageDetectorProxy.getInstance();
        cdp.add(JChardetFacade.getInstance());// 依赖jar包 ：antlr.jar & chardet.jar
        cdp.add(ASCIIDetector.getInstance());
        cdp.add(UnicodeDetector.getInstance());
        cdp.add(new ParsingDetector(false));
        cdp.add(new ByteOrderMarkDetector());
        
        Charset charset = null;
        try {
            charset = cdp.detectCodepage(new URL(url));
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println(charset);
        return charset == null ? null : charset.name().toLowerCase();
    }
    
    /**
     * 根据网页内容获取页面编码
     *     case : 适用于不可以直接读取网页的情况,通过将该网页转换为支持mark的输入流,然后解析编码
     * @param strUrl
     * @return
     */
    public static String getEncodingByContentStream(String strUrl) {
        Charset charset = null;
        try {
            URLConnection urlConn = new URL(strUrl).openConnection();
            //打开链接,加上User-Agent,避免被拒绝
            urlConn.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36");
            
            //解析页面内容
            CodepageDetectorProxy cdp = CodepageDetectorProxy.getInstance();
            cdp.add(JChardetFacade.getInstance());// 依赖jar包 ：antlr.jar & chardet.jar
            cdp.add(ASCIIDetector.getInstance());
            cdp.add(UnicodeDetector.getInstance());
            cdp.add(new ParsingDetector(false));
            cdp.add(new ByteOrderMarkDetector());
            
            InputStream in = urlConn.getInputStream();
            ByteArrayInputStream bais = new ByteArrayInputStream(IOUtils.toByteArray(in));
            // detectCodepage(InputStream in, int length) 只支持可以mark的InputStream
            charset = cdp.detectCodepage(bais, 2147483647);
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return charset == null ? null : charset.name().toLowerCase();
    }
}

mvn install:install-file -Dfile=jar包的位置 -DgroupId=该jar的groupId -DartifactId=该jar的artifactId -Dversion=该jar的version -Dpackaging=jar

<!-- charset detector -->
<dependency>
    <groupId>info.monitorenter.cpdetector</groupId>
    <artifactId>cpdetector</artifactId>
    <version>1.0.10</version>
</dependency>

<!-- antlr -->
<dependency>
    <groupId>antlr</groupId>
    <artifactId>antlr</artifactId>
    <version>2.7.7</version>
</dependency>
<!-- ChardetFacade -->
<dependency>
    <groupId>net.sourceforge.jchardet</groupId>
    <artifactId>jchardet</artifactId>
    <version>1.0</version>
</dependency>