java提供的類庫，並不是一切都能支援你現有的功能的，要敢於編寫自己的類。

　　又是老問題了，我以前一直不敢做，然而現在不得不作了。什麼事情呢？

　　在ｊａｖａ發送郵件時，需要添加附件，然而，我沒有機會添加真是的檔案，只有資料流，因為我是從資料庫中得到的檔案資料流，也來不及放到硬碟上，然而，ｊａｖａｍａｉｌ只支援ＦｉｌｅＳｏｕｒｃｅＤａｔａ的發送，怎麼辦？於是，我就反編譯了其代碼，並修改了自己需要的介面，然後實現了讓其發送ｂｌｏｂ格式檔案的ＢｌｏｂＳｏｕｒｃｅＤａｔａ。帶碼入下，內容很簡單，但是，卻是我邁出的一大步。給我增加了不少自信。

　　

/* * BlobDataSource.java * * Created on 2008.7.9, am11:48 * * To change this template, choose Tools | Template Manager * and open the template in the editor. */package mail;import java.io.InputStream;import java.io.OutputStream;import java.io.File;import java.io.FileDescriptor;import java.io.FileNotFoundException;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.sql.SQLException;import javax.activation.*;import oracle.sql.BLOB;import com.sun.activation.registries.MimeTypeFile;public class BlobDataSource implements DataSource {        private BLOB _blob = null;    private FileTypeMap typeMap = null;    private String _fileName = null;        public BlobDataSource(String fileName, BLOB blob) {        _fileName = fileName;        _blob = blob;    }        /**     * This method will return an InputStream representing the     * the data and will throw an IOException if it can     * not do so. This method will return a new     * instance of InputStream with each invocation.     *     * @return an InputStream     */    public InputStream getInputStream() throws IOException {        try{            return _blob.getBinaryStream();        }catch(SQLException expection){            return null;        }    }        /**     * This method will return an OutputStream representing the     * the data and will throw an IOException if it can     * not do so. This method will return a new instance of     * OutputStream with each invocation.     *     * @return an OutputStream     */    public OutputStream getOutputStream() throws IOException {        try{            return _blob.getBinaryOutputStream();        }catch(SQLException expection){            return null;        }    }        /**     * This method returns the MIME type of the data in the form of a     * string. This method uses the currently installed FileTypeMap. If     * there is no FileTypeMap explictly set, the FileDataSource will     * call the getDefaultFileTypeMap method on     * FileTypeMap to acquire a default FileTypeMap. Note: By     * default, the FileTypeMap used will be a MimetypesFileTypeMap.     *     * @return the MIME Type     * @see javax.activation.FileTypeMap#getDefaultFileTypeMap     */    public String getContentType() {        return "application/octet-stream";    }        /**     * Return the name of this object. The FileDataSource     * will return the file name of the object.     *     * @return the name of the object.     * @see javax.activation.DataSource     */    public String getName() {        return _fileName;    }        /**     * Return the File object that corresponds to this FileDataSource.     * @return the File object for the file represented by this object.     */    public File getFile() {        return null;    }        /**     * Set the FileTypeMap to use with this FileDataSource     *     * @param map The FileTypeMap for this object.     */    public void setFileTypeMap(FileTypeMap map) {        typeMap = map;    }}
 
 
其調用帶碼如下：
    public boolean addFileAffix(String filename,BLOB blob) {                Logger.println("add file affix:" + filename);                try {                        BodyPart bp = new MimeBodyPart();                        BlobDataSource streamds = new BlobDataSource(filename,blob);                        bp.setDataHandler(new DataHandler(streamds));                        bp.setFileName(streamds.getName());                        mp.addBodyPart(bp);                        return true;                    } catch (Exception e) {                        System.err.println("add file affix:" + filename + " error ecured" + e);                        return false;                    }            }