首先自定义一个handler用来处理blob和string之间的转换

import java.io.ByteArrayInputStream;

import java.io.UnsupportedEncodingException;

import java.sql.Blob;

import java.sql.CallableStatement;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.apache.ibatis.type.BaseTypeHandler;

import org.apache.ibatis.type.JdbcType;

/**

* 项目名称：

*

* @description:

*

* @author spg

*

* @create_time：2014年7月24日 下午8:49:02

*

* @version V1.0.0

*

*/

public class MyBlobTypeHandler extends BaseTypeHandler

{

private static final Log LOGGER = LogFactory

.getLog(MyBlobTypeHandler.class);

// 指定字符集

private static final String DEFAULT_CHARSET = "utf-8";

@Override

public void setNonNullParameter(PreparedStatement ps, int i,

String parameter, JdbcType jdbcType) throws SQLException

{

ByteArrayInputStream bis;

try

{

// 把String转化成byte流

bis = new ByteArrayInputStream(parameter.getBytes(DEFAULT_CHARSET));

} catch (UnsupportedEncodingException e)

{

throw new RuntimeException("Blob Encoding Error!");

}

ps.setBinaryStream(i, bis, parameter.length());

}

@Override

public String getNullableResult(ResultSet rs, String columnName)

throws SQLException

{

Blob blob = rs.getBlob(columnName);

byte[] returnValue = null;

String result = null;

if (null != blob)

{

returnValue = blob.getBytes(1, (int) blob.length());

}

try

{

if (null != returnValue)

{

// 把byte转化成string

result = new String(returnValue, DEFAULT_CHARSET);

}

} catch (UnsupportedEncodingException e)

{

throw new RuntimeException("Blob Encoding Error!");

}

return result;

}

@Override

public String getNullableResult(CallableStatement cs, int columnIndex)

throws SQLException

{

Blob blob = cs.getBlob(columnIndex);

byte[] returnValue = null;

String result = null;

if (null != blob)

{

returnValue = blob.getBytes(1, (int) blob.length());

}

try

{

if (null != returnValue)

{

result = new String(returnValue, DEFAULT_CHARSET);

}

} catch (UnsupportedEncodingException e)

{

throw new RuntimeException("Blob Encoding Error!");

}

return result;

}

/**

* @Description:

*

* @param arg0

* @param arg1

* @return

* @throws SQLException

*

* @see org.apache.ibatis.type.BaseTypeHandler#getNullableResult(java.sql.ResultSet,

* int)

*

*/

@Override

public String getNullableResult(ResultSet rs, int columnName)

throws SQLException

{

LOGGER.debug("enter function");

String result = null;

Blob blob = rs.getBlob(columnName);

byte[] returnValue = null;

if (null != blob)

{

returnValue = blob.getBytes(1, (int) blob.length());

}

try

{

// 把byte转化成string

if (null != returnValue)

{

result = new String(returnValue, DEFAULT_CHARSET);

}

} catch (UnsupportedEncodingException e)

{

throw new RuntimeException("Blob Encoding Error!");

}

LOGGER.debug("exit function");

return result;

}

}resultMap中添加handler配置，如下：

OK！这样查出来的结果就是string类型

同理，如果对与枚举类型也可通过此方式进行转换！