mybatis 处理CLOB/BLOB类型数据

BLOB和CLOB都是大字段类型。java

BLOB是按二进制来存储的，而CLOB是能够直接存储文字的。sql

一般像图片、文件、音乐等信息就用BLOB字段来存储，先将文件转为二进制再存储进去。文章或者是较长的文字，就用CLOB存储.数据库

BLOB和CLOB在不一样的数据库中对应的类型也不同:
MySQL 中：clob对应text/longtext，blob对应blob
Oracle中：clob对应clob，blob对应blob

MyBatis提供了内建的对CLOB/BLOB类型列的映射处理支持。app

建表语句：测试

create table user_pics( id number primary key, name varchar2(50) , pic blob, bio clob );

照片（pic）能够是PNG,JPG或其余格式的。简介信息（bio）能够是学比较长的文字描述。默认状况下，MyBatis将CLOB类型的列映射到java.lang.String类型上、而把BLOB列映射到byte[]类型上。spa

public class UserPic{ private int id; private String name; private byte[] pic; private String bio; //setters & getters 
}

映射文件：code

<insert id="insertUserPic" parameterType="UserPic"> 
            <selectKey keyProperty="id" resultType="int" order="BEFORE"> select my_seq.nextval from dual </selectKey> insert into user_pics(id,name, pic,bio) values(#{id},#{name},#{pic},#{bio}) </insert> 

        <select id="getUserPicById" parameterType="int" resultType="UserPic"> select * from user_pics where id=#{id} </select>

映射接口：对象

public interface PicMapper { int insertUserPic(UserPic userPic); UserPic getUserPicById(int id); }

测试方法:blog

public void test_insertUserPic(){ String name = "tom"; String bio = "能够是很长的字符串"; byte[] pic = null; try { //读取用户头像图片
                File file = new File("src/com/briup/special/1.gif"); InputStream is = new FileInputStream(file); pic = new byte[is.available()]; is.read(pic); is.close(); } catch (Exception e){ e.printStackTrace(); } //准备好要插入到数据库中的数据并封装成对象
            UserPic userPic = new UserPic(name, pic , bio); SqlSession sqlSession = null; try{ sqlSession = MyBatisSqlSessionFactory.openSession(); SpecialMapper mapper = sqlSession.getMapper(SpecialMapper.class); mapper.insertUserPic(userPic); sqlSession.commit(); }catch (Exception e) { e.printStackTrace(); } }

下面的getUserPic()方法将CLOB类型数据读取到String类型，BLOB类型数据读取成byte[]属性：接口

@Test public void test_getUserPicById(){ SqlSession sqlSession = null; try { sqlSession = MyBatisSqlSessionFactory.openSession(); SpecialMapper mapper = sqlSession.getMapper(SpecialMapper.class); UserPic userPic = mapper.getUserPicById(59); System.out.println(userPic.getId()); System.out.println(userPic.getName()); System.out.println(userPic.getBio()); System.out.println(userPic.getPic().length); } catch (Exception e) { e.printStackTrace(); } }