Question

如何从ORACLE中读取CLOB类型的数据

Answer 1

MyBatis 本是apache的一个开源项目iBatis, 2010年这个项目由apache software foundation 迁移到了google code，并且改名为MyBatis 。2013年11月迁移到Github。
iBATIS一词来源于“internet”和“abatis”的组合，是一个基于Java的持久层框架。iBATIS提供的持久层框架包括SQL Maps和Data Access Objects（DAO）
2、CLOB
SQL CLOB 是内置类型，它将字符大对象 (Character Large Object) 存储为数据库表某一行中的一个列值。默认情况下，驱动程序使用 SQL locator(CLOB) 实现 Clob 对象，这意味着 CLOB 对象包含一个指向 SQL CLOB 数据的逻辑指针而不是数据本身。Clob 对象在它被创建的事务处理期间有效。
3、MyBatis对CLOB类型数据实现增删改查
oracle表结构

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create table T_USERS
(
ID NUMBER not null,
NAME VARCHAR2(30),
SEX VARCHAR2(3),
BIRS DATE,
MESSAGE CLOB
)
create sequence SEQ_T_USERS_ID
minvalue 1
maxvalue 99999999
start with 1
increment by 1
cache 20;

配置mybatis配置文件UsersMapper.xml

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN">

<mapper namespace="examples.mapper.UsersMapper" >

<!-- Result Map-->
<resultMap type="examples.bean.Users" id="BaseResultMap">
<result property="id" column="id" />
<result property="name" column="name" />
<result property="sex" column="sex" />
<result property="birs" column="birs" jdbcType="TIMESTAMP"/>
<result property="message" column="message" jdbcType="CLOB"
javaType = "java.lang.String" typeHandler ="examples.service.OracleClobTypeHandler"/>
</resultMap>

<sql id="Tabel_Name">
t_users
</sql>

<!-- 表中所有列 -->
<sql id="Base_Column_List" >
id,name,sex,birs,message
</sql>

<!-- 查询条件 -->
<sql id="Example_Where_Clause">
where 1=1
<trim suffixOverrides=",">
<if test="id != null">
and id = #{id}
</if>
<if test="name != null and name != ''">
and name like concat(concat('%', '${name}'), '%')
</if>
<if test="sex != null and sex != ''">
and sex like concat(concat('%', '${sex}'), '%')
</if>
<if test="birs != null">
and birs = #{birs}
</if>
<if test="message != null">
and message = #{message}
</if>
</trim>
</sql>

<!-- 2.查询列表 -->
<select id="queryByList" resultMap="BaseResultMap" parameterType="Object">
select
<include refid="Base_Column_List" />
from t_users
<include refid="Example_Where_Clause"/>
</select>
</mapper>

Mapper类接口

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package examples.mapper;

import java.util.List;

public interface UsersMapper<T> {

public List<T> queryBySelective(T t);

public List<T> queryByList(T t);

}

类型转换工具类

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package examples.service;

import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import oracle.sql.CLOB;

import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.TypeHandler;

public class OracleClobTypeHandler implements TypeHandler<Object> {

public Object valueOf(String param) {
return null;
}

@Override
public Object getResult(ResultSet arg0, String arg1) throws SQLException {
CLOB clob = (CLOB) arg0.getClob(arg1);
return (clob == null || clob.length() == 0) ? null : clob.getSubString((long) 1, (int) clob.length());
}

@Override
public Object getResult(ResultSet arg0, int arg1) throws SQLException {
return null;
}

@Override
public Object getResult(CallableStatement arg0, int arg1) throws SQLException {
return null;
}

@Override
public void setParameter(PreparedStatement arg0, int arg1, Object arg2, JdbcType arg3) throws SQLException {
CLOB clob = CLOB.empty_lob();
clob.setString(1, (String) arg2);
arg0.setClob(arg1, clob);
}
}

Spring配置文件

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="

xmlns:xsi="

xmlns:mvc="
xmlns:tx="
xsi:schemaLocation="
default-autowire="byType">

<!-- 配置数据源 -->
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName"><value>oracle.jdbc.driver.OracleDriver</value></property>
<property name="url"><value>jdbc:oracle:thin:@127.0.0.1:1521:pms</value></property>
<property name="username"><value>pms</value></property>
<property name="password"><value>pms</value></property>
</bean>

<!-- 配完数据源 和 拥有的 sql映射文件 sqlSessionFactory 也可以访问数据库 和拥有 sql操作能力了 -->
<!--
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="configLocation" value="classpath:mybatis-config.xml"/>
</bean>
-->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="mapperLocations">
<list>
<value>classpath:examples/mybatis/oracle/UsersMapper.xml</value>
</list>
</property>
</bean>

<!-- 通过设置 mapperInterface属性，使接口服务bean 和对应xml文件管理 可以使用其中的sql -->
<bean id="dao" class="org.mybatis.spring.mapper.MapperFactoryBean">
<!-- 此处等同于 Mybatis 中 ServerDao serverDao = sqlSession.getMapper(ServerDao.class); 指明映射关系 -->
<property name="mapperInterface" value="examples.mapper.UsersMapper" />
<property name="sqlSessionFactory" ref="sqlSessionFactory" />
</bean>
</beans>

测试类

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package examples.service;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.List;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import examples.bean.Users;
import examples.mapper.UsersMapper;

public class TestUsersService {

@SuppressWarnings("unchecked")
public static void main(String[] args) throws ParseException {
ApplicationContext ac =
new ClassPathXmlApplicationContext("classpath:/examples/service/spring.xml");
UsersMapper<Users> dao = (UsersMapper<Users>)ac.getBean("dao");

//查询
Users nullBean = new Users();
List<Users> list = dao.queryByList(nullBean);
if(list != null) {
for(Users user : list) {
System.out.println(user);
}
}

}

}