Hibernate操作Blob，将Blob转换为String

public String getScenicCoord(String pk) {
log.debug("根据景区唯一标示获取景区坐标!");
String sql = "select wkt from JQGEO where id = '" + pk + "'";
String result = "";
try {
Connection conn = getSession().connection();
PreparedStatement ps = conn.prepareStatement(sql);
ResultSet set = ps.executeQuery();
if(set.next()) {
Blob blob = set.getBlob(1);
//这种方式看起来没有什么问题，但是数据类型及参数未知的错误会在莫名的情况下出现
//int len = (int)blob.length();
//byte[] bt = blob.getBytes(0, len);
//String str = new String(bt);

//这种转换后的方式倒是能够正常的将二进制流转换为String类型数据
InputStream in = blob.getBinaryStream();
int size = in.available();
byte[] by = new byte[size];
in.read(by);
result = new String(by);
}
}catch (Exception e) {
log.error("根据景区唯一标示获取景区坐标失败!");
result = null;
try {
throw e;
} catch (Exception e1) {
e1.printStackTrace();
result = null;
}
}
return result;
}