使用mybatis的typeHandler对clob进行流读写

分为三步：

第一步：编写typehandler文件：

package com.dcits.edps.common.utils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.Writer;
import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.MappedJdbcTypes;
import org.apache.ibatis.type.MappedTypes;
import org.springframework.util.FileCopyUtils;

/** 
 * 
标题：处理Clob字段
 * 
描述：使用流对Clob字段进行读写
 * 
编译者：zt
 * 
版本：1.0
 */
 @MappedTypes({String.class})
 @MappedJdbcTypes({JdbcType.CLOB})
 public class OscarClobTypeHandler extends BaseTypeHandler {
	@Override
	public void setNonNullParameter(PreparedStatement ps, int i, String parameter, JdbcType jdbcType)
			throws SQLException {
		final StringReader sr = new StringReader(parameter);
		final int length = parameter.getBytes().length;
		ps.setCharacterStream(i, sr, length);
		sr.close();
		
	}

	@Override
	public String getNullableResult(ResultSet rs, String columnName) throws SQLException {
		final OutputStream outPutStream = new ByteArrayOutputStream();
		final Writer writer = new OutputStreamWriter(outPutStream);
		try {
			Reader reader = rs.getCharacterStream(columnName);
			if(null == reader){
				return null;
			}else {
				FileCopyUtils.copy(reader, writer);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
		return outPutStream.toString();
	}

	@Override
	public String getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
		final OutputStream outPutStream = new ByteArrayOutputStream();
		final Writer writer = new OutputStreamWriter(outPutStream);
		try {
			Reader reader = rs.getCharacterStream(columnIndex);
			if(null == reader){
				return null;
			}else {
				FileCopyUtils.copy(reader, writer);
			} 
		}catch (IOException e) {
			e.printStackTrace();
		}
		return outPutStream.toString();
	}

	@Override
	public String getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
		final OutputStream outPutStream = new ByteArrayOutputStream();
		final Writer writer = new OutputStreamWriter(outPutStream);
		try {
			Reader reader = cs.getCharacterStream(columnIndex);
			if(null == reader){
				return null;
			}else {
				FileCopyUtils.copy(reader, writer);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
		return outPutStream.toString();
	}

 }

第二步：在mybatis的配置文件中添加节点。需要注意的是，mybatisd的配置文件中的节点中的子节点需要有顺序，顺序为：properties—>settings—>typeAliases—>typeHandlers—>objectFactory—>objectWrapperFactory—>plugins—>environments—>databaseIdProvider—>mappers。

第三步：

               ①在resultMap中需要添加jdbcType，这是在读取时使用了流，如下所示

             ② 在写入数据的时候使用：

          

        fsfh=#{fsfh,jdbcType=CLOB}