java使用jchardet检测文本文件(字节流)的编码方式

有时需要InputStreamReader(InputStream in, Charset cs)这个构造来处理字符流。然而Charset不一定知道。这个时候就需要检测编码方式了。jchardet是firefox使用的字节流编码检测算法的java开源实现，协议为MPL(Mozilla Public License)，对商业友好。下载源代码后发现示例并不怎么好使用，于是封装了一下。下面就封装类和使用Demo。

 

CharsetDetector 这个封装了内部实现，用户直接new这个类就可以检测字节流编码

 

package cn.xddai.chardet;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import org.mozilla.intl.chardet.nsDetector;
import org.mozilla.intl.chardet.nsICharsetDetectionObserver;
import org.mozilla.intl.chardet.nsPSMDetector;

/**
 *
 * @author xddai
 */
public class CharsetDetector
{

    private boolean found = false;
    private String result;
    private int lang;

    public String[] detectChineseCharset(InputStream in) throws IOException
    {
        lang = nsPSMDetector.CHINESE;
        String[] prob;
        // Initalize the nsDetector() ;
        nsDetector det = new nsDetector(lang);
        // Set an observer...
        // The Notify() will be called when a matching charset is found.

        det.Init(new nsICharsetDetectionObserver()
        {

            public void Notify(String charset)
            {
                found = true;
                result = charset;
            }
        });
        BufferedInputStream imp = new BufferedInputStream(in);
        byte[] buf = new byte[1024];
        int len;
        boolean isAscii = true;
        while ((len = imp.read(buf, 0, buf.length)) != -1)
        {
            // Check if the stream is only ascii.
            if (isAscii)
                isAscii = det.isAscii(buf, len);
            // DoIt if non-ascii and not done yet.
            if (!isAscii)
            {
                if (det.DoIt(buf, len, false))
                    break;
            }
        }
        imp.close();
        in.close();
        det.DataEnd();
        if (isAscii)
        {
            found = true;
            prob = new String[]
                    {
                        "ASCII"
                    };
        } else if (found)
        {
            prob = new String[]
                    {
                        result
                    };
        } else
        {
            prob = det.getProbableCharsets();
        }
        return prob;
    }

    public String[] detectAllCharset(InputStream in) throws IOException
    {
        try
        {
            lang = nsPSMDetector.ALL;
            return detectChineseCharset(in);
        } catch (IOException e)
        {
            throw e;
        }
    }
}

 

 

Demo:这个演示CharsetDetector用法示例

 

package cn.xddai.chardet;

import java.io.IOException;
import java.net.URL;

/**
 *
 * @author xddai
 */
public class Demo
{
    public static void main(String[] args)throws IOException
    {
        CharsetDetector charDect = new CharsetDetector();
        URL url = new URL("http://www.qq.com/");
        String[] probableSet = charDect.detectChineseCharset(url.openStream());
        for (String charset : probableSet)
        {
            System.out.println(charset);
        }
    }
}

  封装后的jar包下载地址http://codeinplatform.googlecode.com/files/CharsetDetector.jar

最后，感谢Mozilla大神为开源做的贡献。