MyBatis读取MySql中BLOB数据

╰半夏微凉° 2022-08-10 15:57 260阅读 0赞

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<String>
    {
    
    	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！