java将byte写入文件 java byte转blob

准备先把以前写的持久层及表示层框架写完再写loonframework-game包(实际上是想自己业余建站用，用现成的框架太无聊，重复发明轮子的最大意义就在于解闷……)，在2005年时写过一个开头，由于自己没有整理文档，现在拿起来就觉得代码很乱，又懒于写文档，于是把一些心得类的东西整理一下，用以备忘。

在此持久层框架中，我将持久化过程分为两个松耦合模块，第一模块封装jdbc操作，隐藏Connection及相关事务，处理driver差异后执行标准CRUD并释放资源，于第二模块进行实体映射操作。

但和Spring JdbcTemplate等jdbc封装略有不同的是，我除了直接将结果集转为List和实体返回外，还引入了一个类似CachedRowSet但非继承CachedRowSet或ResultSet的结果集cache实体（没有提供诸如CachedRowSet的execute功能，原因大家都知道……PS:05年我用Hibernate还比较少，现在看来和Hierbante的ScrollableResults接口超级类似，颇感java技术殊途同归|||）。

但在此类get数据时，由于我将所有ResultSet数据无差别以object方式存储，当object为二进制对象时，为实现blob和clob接口就需要进行数据转换，将二进制对象转为blob或clob实现，为此完成代码如下。

比较hibernate的blobimpl而言（hibernate的blobimpl只有getBinaryStream()实现，因为别的对它也没用……），实现了更多的函数以供调用。

BlobImpl.java
package org.loon.framework.dao.lob;

import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

import java.io.OutputStream;
import java.sql.Blob;
import java.sql.SQLException;

import org.loon.framework.Loon;
import org.loon.framework.helper.FileHelper;

/** *//**
 * <p>
 * Title: LoonFramework
 * </p>
 * <p>
 * Description:二进制大对象Blob实现，用于转化二进制对象为blob实例，只提供get部分方法(虽然象征性的写了
 * set实现，但没有对数据库进行操作，只是摆设……).
 * </p>
 * <p>
 * Copyright: Copyright (c) 2007
 * </p>
 * <p>
 * Company: LoonFramework
 * </p>
 * <p>
 * License: http://www.apache.org/licenses/LICENSE-2.0
 * </p>
 * 
 * @author chenpeng
 * @email：[e-mail]
 * @version 0.1
 */
public class BlobImpl implements Blob ...{


    private byte[] _bytes = new byte[0];

    private int _length = 0;

    /** *//**
     * 构造函数，以byte[]构建blob
     * 
     * @param bytes
     */
    public BlobImpl(byte[] bytes) ...{
        init(bytes);
    }

    /** *//**
     * 构造函数，以InputStream构建blob
     * 
     * @param bytes
     */
    public BlobImpl(InputStream input) ...{
        init(FileHelper.read(input));
    }

    /** *//**
     * 构造函数，以blob重新构建blob
     * 
     * @param bytes
     */
    public BlobImpl(Blob blob) ...{
        init(blobToBytes(blob));
    }

    /** *//**
     * 初始化byte[]
     * 
     * @param b
     */
    private void init(byte[] bytes) ...{
        _bytes = bytes;
        _length = _bytes.length;
    }

    /** *//**
     * 将blob转为byte[]
     * 
     * @param blob
     * @return
     */
    private byte[] blobToBytes(Blob blob) ...{
        BufferedInputStream is = null;
        try ...{
            is = new BufferedInputStream(blob.getBinaryStream());
            byte[] bytes = new byte[(int) blob.length()];
            int len = bytes.length;
            int offset = 0;
            int read = 0;
            while (offset < len
                    && (read = is.read(bytes, offset, len - offset)) >= 0) ...{
                offset += read;
            }
            return bytes;
        } catch (Exception e) ...{
            return null;
        } finally ...{
            try ...{
                is.close();
                is = null;
            } catch (IOException e) ...{
                return null;
            }

        }
    }

    /** *//**
     * 获得blob中数据实际长度
     * 
     * @return
     * @throws SQLException
     */
    public long length() throws SQLException ...{
        return _bytes.length;
    }

    /** *//**
     * 返回指定长度的byte[]
     * 
     * @param pos
     * @param len
     * @return
     * @throws SQLException
     */
    public byte[] getBytes(long pos, int len) throws SQLException ...{
        if (pos == 0 && len == length())
            return _bytes;
        try ...{
            byte[] newbytes = new byte[len];
            System.arraycopy(_bytes, (int) pos, newbytes, 0, len);
            return newbytes;
        } catch (Exception e) ...{
            throw new SQLException("Inoperable scope of this array");
        }
    }

    /** *//**
     * 返回InputStream
     * 
     * @return
     * @throws SQLException
     */
    public InputStream getBinaryStream() throws SQLException ...{
        return new ByteArrayInputStream(_bytes);
    }

    /** *//**
     * 获取此byte[]中start的字节位置
     * 
     * @param pattern
     * @param start
     * @return
     * @throws SQLException
     */
    public long position(byte[] pattern, long start) throws SQLException ...{
        start--;
        if (start < 0) ...{
            throw new SQLException("start < 0");
        }
        if (start >= _length) ...{
            throw new SQLException("start >= max length");
        }
        if (pattern == null) ...{
            throw new SQLException("pattern == null");
        }
        if (pattern.length == 0 || _length == 0 || pattern.length > _length) ...{
            return -1;
        }
        int limit = (int) _length - pattern.length;
        for (int i = (int) start; i <= limit; i++) ...{
            int p;
            for (p = 0; p < pattern.length && _bytes[i + p] == pattern[p]; p++) ...{
                if (p == pattern.length) ...{
                    return i + 1;
                }
            }
        }
        return -1;
    }

    /** *//**
     * 获取指定的blob中start的字节位置
     * 
     * @param pattern
     * @param start
     * @return
     * @throws SQLException
     */
    public long position(Blob pattern, long start) throws SQLException ...{
        return position(blobToBytes(pattern), start);
    }

    /** *//**
     * 不支持操作异常抛出
     * 
     */
    void nonsupport() ...{
        throw new UnsupportedOperationException("This method is not supported！");
    }

    /** *//**
     * 释放Blob对象资源
     * 
     * @throws SQLException
     */
    public void free() throws SQLException ...{
        _bytes = new byte[0];
        _length = 0;
    }

    /** *//**
     * 返回指定长度部分的InputStream，并返回InputStream
     * 
     * @param pos
     * @param len
     * @return
     * @throws SQLException
     */
    public InputStream getBinaryStream(long pos, long len) throws SQLException ...{
        return new ByteArrayInputStream(getBytes(pos, (int) len));
    }

    /** *//**
     * 以指定指定长度将二进制流写入OutputStream，并返回OutputStream
     * 
     * @param pos
     * @return
     * @throws SQLException
     */
    public OutputStream setBinaryStream(long pos) throws SQLException ...{
        // 暂不支持
        nonsupport();
        pos--;
        if (pos < 0) ...{
            throw new SQLException("pos < 0");
        }
        if (pos > _length) ...{
            throw new SQLException("pos > length");
        }
        // 将byte[]转为ByteArrayInputStream
        ByteArrayInputStream inputStream = new ByteArrayInputStream(_bytes);
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        byte[] bytes = new byte[(int) pos];
        try ...{
            bytes = new byte[inputStream.available()];
            int read;
            while ((read = inputStream.read(bytes)) >= 0) ...{
                os.write(bytes, 0, read);
            }

        } catch (IOException e) ...{
            e.getStackTrace();
        }

        // 返回OutputStream
        return (OutputStream) os;
    }

    /** *//**
     * 设定byte[]
     * 
     * @param pos
     * @param bytes
     * @param offset
     * @param size
     * @param copy
     * @return
     * @throws SQLException
     */
    private int setBytes(long pos, byte[] bytes, int offset, int size,
            boolean copy) throws SQLException ...{
        // 暂不支持
        nonsupport();
        pos--;
        if (pos < 0) ...{
            throw new SQLException("pos < 0");
        }
        if (pos > _length) ...{
            throw new SQLException("pos > max length");
        }
        if (bytes == null) ...{
            throw new SQLException("bytes == null");
        }
        if (offset < 0 || offset > bytes.length) ...{
            throw new SQLException("offset < 0 || offset > bytes.length");
        }
        if (size < 0 || pos + size > (long) Integer.MAX_VALUE
                || offset + size > bytes.length) ...{
            throw new SQLException();
        }
        // 当copy数据时
        if (copy) ...{
            _bytes = new byte[size];
            System.arraycopy(bytes, offset, _bytes, 0, size);
        } else ...{ // 否则直接替换对象
            _bytes = bytes;
        }
        return _bytes.length;
    }

    /** *//**
     * 设定指定开始位置byte[]
     * 
     * @param pos
     * @param bytes
     * @return
     * @throws SQLException
     */
    public int setBytes(long pos, byte[] bytes) throws SQLException ...{
        // 暂不支持
        nonsupport();
        return setBytes(pos, bytes, 0, bytes.length, true);
    }

    /** *//**
     * 设定byte[]
     * 
     * @param pos
     * @param bytes
     * @param offset
     * @param len
     * @return
     * @throws SQLException
     */
    public int setBytes(long pos, byte[] bytes, int offset, int len)
            throws SQLException ...{
        // 暂不支持
        nonsupport();
        return setBytes(pos, bytes, offset, len, true);
    }

    /** *//**
     * 截取相应部分数据
     * 
     * @param len
     * @throws SQLException
     */
    public void truncate(long len) throws SQLException ...{
        if (len < 0) ...{
            throw new SQLException("len < 0");
        }
        if (len > _length) ...{
            throw new SQLException("len > max length");
        }
        _length = (int) len;
    }

    public static void main(String[] args) ...{

        //获得一个指定文件的blob
        //PS:天地良心啊，没抄袭hibernate写法，无奈的写一样了，不过比他多实现了点方法……（还特意把函数改名，不然更像|||）……
        Blob blob = Loon.makeBlob("D:/test.txt"); 
        // 以byte[]获得blob实例
        //Blob blob = new BlobImpl(bytes);
        try ...{
            // getBytes测试
            // 取出0到blob结束范围的byte[]
            byte[] buffer = blob.getBytes(0, (int) blob.length());
            // 以gb2312编码将byte[]转为string显示
            System.out.println(new String(buffer, "gb2312"));

            // getBinaryStream测试
            BufferedInputStream is = new BufferedInputStream(blob
                    .getBinaryStream());
            buffer = new byte[(int) blob.length()];
            int len = buffer.length;
            int offset = 0;
            int read = 0;
            while (offset < len
                    && (read = is.read(buffer, offset, len - offset)) >= 0) ...{
                offset += read;
            }
            System.out.println(new String(buffer, "gb2312"));

            // getBinaryStream范围取值测试,取0to4的byte[]
            is = new BufferedInputStream(blob.getBinaryStream(0, 4));
            //将is转为byte[]后转为String显示
            System.out.println(FileHelper.readToString(is, "gb2312"));

        } catch (Exception e) ...{
            e.printStackTrace();
        }

    }

}