java String与Blob类型数据转换

需要把String类型数据转换成Reader，然后再使用setCharacterStream插入数据库中。

例如下例中，要插入String longStr，则先转换成Byte[]，再ByteArrayInputStream，最后InputStreamReader。

添加或更新clob型数据，如下所示（以更新为例）： 

 
  PreparedStatement pstmt=conn.prepareStatement(“update tablename set column1=? “+条件语句);  
  byte[] bytes_zyjs = longStr.getBytes();  
  ByteArrayInputStream baisss = new ByteArrayInputStrea(bytes_zyjs);  
  InputStreamReader bais = new InputStreamReader(baisss);  
  pstmt.setCharacterStream(1,bais,bytes_zyjs.length);  
  pstmt.executeUpdate();  

但是如上方式写入汉字就会产生乱码，于是查看资料得知，上述方法多用于oracle下，而mysql下使用的是setBinaryStream方法，只要传入位置，inputstream，和长度即可。示例如下：

byte[] cert_dataBytes = cert_data.getBytes();
  ByteArrayInputStream bais1 = new ByteArrayInputStream(cert_dataBytes);
  byte[] prikey_dataBytes = prikey_data.getBytes();
  ByteArrayInputStream bais2 = new ByteArrayInputStream(prikey_dataBytes);
  String sql = "insert into cert_data values(?,?,?)";
  PreparedStatement pstm = null;
  try {
   conn.setAutoCommit(false);
   pstm = conn.prepareCall(sql);
   pstm.setInt(1,cert_sn);
   pstm.setBinaryStream(2, bais1,cert_dataBytes.length);//使用二进制读取，可以直接写入汉字，否则容易产生乱码
   pstm.setBinaryStream(3, bais2, prikey_dataBytes.length);
   pstm.executeUpdate();
   conn.commit();
   conn.setAutoCommit(true);
   pstm.close(); 
  } catch (SQLException e) {
   e.printStackTrace();
  }finally{
    try {
     if(pstm != null)
      pstm.close();
    } catch (SQLException e) {
     e.printStackTrace();
    }
  }
//从数据库中读取Blob类型数据后，要转换成String类型，即转换成InputStream，再从InputStream转成byte[]，再到String即可。如下：
//把数据库中blob类型转换成String类型
 public String convertBlobToString(Blob blob){ 
  String result = "";
  try {
   ByteArrayInputStream msgContent =(ByteArrayInputStream) blob.getBinaryStream();
   byte[] byte_data = new byte[msgContent.available()];
   msgContent.read(byte_data, 0,byte_data.length);
   result = new String(byte_data);
  } catch (SQLException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  return result;
 }

2批量插入 带blob类型的实体类

public void insertBatchList(ArrayList list) {
		Connection conn = null;
		PreparedStatement stmt = null;
		MetadataMapVo vo = null;
		try {
			conn = DAOUtils.getDBConnection(JNDINames.CRM_DATASOURCE, this);
			stmt = conn.prepareStatement(DAOSQLUtils.getFilterSQL(SQL_INSERT));
			
			if (list != null && list.size() > 0) {
				for (int i = 0; i < list.size(); i++) {
					vo = (MetadataMapVo) list.get(i);
					int index = 1;
					stmt.setString( index++, ((MetadataMapVo)vo).getId() );
					stmt.setString( index++, ((MetadataMapVo)vo).getInterc_type());
					stmt.setString( index++, ((MetadataMapVo)vo).getInterc_metadata_id() );
					stmt.setString( index++, ((MetadataMapVo)vo).getSource_type() );
					stmt.setString( index++, ((MetadataMapVo)vo).getSource_id() );
					stmt.setString( index++, ((MetadataMapVo)vo).getTarget_type() );
					stmt.setString( index++, ((MetadataMapVo)vo).getTarget_id() );
					String desc =((MetadataMapVo)vo).getDescription();
					if(!StringUtil.isEmptyOrNull(desc)){
						ByteArrayInputStream is = new ByteArrayInputStream(desc.getBytes());
						stmt.setBinaryStream( index++, is,desc.getBytes().length);
					}else{
						stmt.setString( index++, null);
					}
					stmt.setString( index++, ((MetadataMapVo)vo).getRequeir_file_path() );
					stmt.setString( index++, ((MetadataMapVo)vo).getStatus());
					stmt.addBatch();
					}
				stmt.executeBatch();
				}
		} catch (SQLException se) {
			Debug.print(SQL_INSERT, this);
			throw new DAOSystemException("SQLException while insert sql:\n" + SQL_INSERT, se);
		} finally {
			DAOUtils.closeStatement(stmt, this);
			DAOUtils.closeConnection(conn, this);
		}
		
	}

查询带blob类型的实体类

private String convertBLOBtoString(Object blobContent) {
		try {
			Class clazz = blobContent.getClass();
			Method method = clazz.getMethod("getBinaryStream",new Class[] {});
			InputStream is = (InputStream) method.invoke(blobContent,new Object[] {});
			ByteArrayOutputStream   baos   =   new   ByteArrayOutputStream(); 
	        int i=-1; 
	        while((i=is.read())!=-1){ 
	        	baos.write(i); 
	        } 
	       return baos.toString(); 
		} catch (Exception e) {
			e.printStackTrace();
		}
		return "";
	}
	private Map rowToMap(ResultSet rs) throws Exception {
		Map result = new HashMap();
		ResultSetMetaData rsmd = rs.getMetaData();
		int cols = rsmd.getColumnCount();
		String type="";
		for (int i = 1; i <= cols; i++) {
			if(rsmd.getColumnName(i).toUpperCase().equals("SOURCE_TYPE")){
				type = rs.getString(i);
			}
			if(rsmd.getColumnName(i).toUpperCase().equals("DESCRIPTION")){
				result.put(rsmd.getColumnName(i).toLowerCase(), this.convertBLOBtoString(rs.getBlob(i)));;
			}else{
				result.put(rsmd.getColumnName(i).toLowerCase(), rs.getString(i));
			}
		}
		if(!type.equals("")){
			if("4".equals(type.trim())||"6".equals(type.trim())){
				String xml=(String) result.get("description");
				Document doc =DocumentHelper.parseText(xml); 
				Element root =  doc.getRootElement();  
				String cal_function = root.attributeValue("cal_function");
				String require_des = root.attributeValue("require_des");
				result.put("cal_function", cal_function);
				result.put("require_des", require_des);
			}
		}
		return result;
	}
	@Override
	public List getBooldData(Map map) throws Exception {
		Connection conn = null;
		PreparedStatement stmt = null;
		ResultSet rs = null;
		List<Map<String,String>> list = null;
		String whereCond ="";
		try {
			whereCond =" where a.interc_type='"+map.get("interc_type")+"' and a.interc_metadata_id='"+map.get("interc_metadata_id")+"'";
			conn = DAOUtils.getDBConnection(JNDINames.CRM_DATASOURCE, this);
			stmt = conn.prepareStatement(DAOSQLUtils.getFilterSQL(SELECT_SQL + whereCond));
			rs = stmt.executeQuery();
			Map<String, String> m = null;
			list = new ArrayList<Map<String,String>>();
			while(rs.next()){
				list.add(this.rowToMap(rs));
			}
		} catch (SQLException se) {
			Debug.print(SELECT_SQL + whereCond, this);
			throw new DAOSystemException("SQLException while getting sql:\n" + SELECT_SQL + whereCond, se);
		} finally {
			DAOUtils.closeResultSet(rs, this);
			DAOUtils.closeStatement(stmt, this);
			DAOUtils.closeConnection(conn, this);
		}
		System.out.println();
		System.out.println(list.size());
		return list;
	}