如何使用Hibernate对Oracle中Clob类型数据存储和取出详解编程语言

一.了解clob使用场景和使用方式：

1.为何实用Clob:  

Oracle数据库当需要存入大数据量（大于4000）时，varchar2不够用，可以使用clob，本文描述clob怎么和hibernate一起使用。

2.Clob类型的属性的赋值方式String转Clob：

String content = request.getParameter(“content”);//1.从request请求中取值（String类型的）

Clob clob = Hibernate.createClob(content);//2.通过hibernate将string转化为clob

news.setContent(clob);//3.给实体类对应属性赋值

3.Clob类型的属性的取值方式Clob转String：

List<News> list = query.addEntity(News.class).list();//1.从数据库取值

News news = (News)list.get(0);//2.取News对象

String content = ClobUtil.ClobToString(news.getContent());//3.将news对象中的clob类型的content转化为String字符串

二.实例分析：

1.建数据表：

2.创建实体类和映射文件：

public class News {

    private Long id;

    private String dir;

    private String fileName;

    private String title;

    private String tag;

    private String imgUrl;

    private Integer type;

    private String creator;

    private Date createDate;

    private String remark;

    private Integer ishot;

    private Clob content;

    //get和set方法省略…

}

hibernate配置文件如下：

<?xml version=”1.0″?>

<!DOCTYPE hibernate-mapping PUBLIC “-//Hibernate/Hibernate Mapping DTD 3.0//EN”

“http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd”>

<!– Generated 2014-11-28 9:58:10 by Hibernate Tools 3.4.0.CR1 –>

<hibernate-mapping>

    <class name=”net.itxm.entity.News” table=”NEWS”>

        <id name=”id” column=”ID”>

            <generator class=”sequence”>

                <param name=”sequence”>SQ_NEWS</param>

            </generator>

        </id>

        <property name=”dir” type=”java.lang.String”>

            <column name=”DIR” />

        </property>

        <property name=”fileName” type=”java.lang.String”>

            <column name=”FILE_NAME” />

        </property>

        <property name=”title” type=”java.lang.String”>

            <column name=”TITLE” />

        </property>

        <property name=”tag” type=”java.lang.String”>

            <column name=”TAG” />

        </property>

        <property name=”imgUrl” type=”java.lang.String”>

            <column name=”IMG_URL” />

        </property>

        <property name=”type” type=”java.lang.Integer”>

            <column name=”TYPE” />

        </property>

        <property name=”creator” type=”java.lang.String”>

            <column name=”CREATOR” />

        </property>

        <property name=”createDate” type=”java.util.Date”>

            <column name=”CREATE_DATE” />

        </property>

        <property name=”remark” type=”java.lang.String”>

            <column name=”REMARK” />

        </property>

         <property name=”ishot” type=”java.lang.Integer”>

            <column name=”ISHOT” />

        </property>

        <property name=”content” type=”java.sql.Clob”>

            <column name=”CONTENT” />

        </property>

    </class>

</hibernate-mapping>

3.增加News的Servlet:需要对String数据转化成Clob数据

String title = request.getParameter(“title”);

String tag = request.getParameter(“tag”);

String content = request.getParameter(“content”);

String typeStr = request.getParameter(“type”);

String ishotStr = request.getParameter(“ishot”);

int type = Integer.valueOf(typeStr);

int ishot = 0;

if(“on”.equals(ishotStr)){

    ishot = 1;

}

Clob clob = Hibernate.createClob(content);

INewsDao newsDao = new NewsDaoImpl();

News news = new News();

news.setDir(htmlDir + detailDir);

news.setFileName(fileName);

news.setCreateDate(createDate);

news.setCreator(user.getUsername());

news.setTitle(title);

news.setTag(tag);

news.setType(type);

news.setIshot(ishot);

news.setContent(clob);

newsDao.saveNews(news);

注意：要对request获取的字符串用hibernate转化为clob类型  

4.从数据库获取news中的Content：—— 需要对String数据转化成Clob数据

public String getNewsContentById(int id) {

    Session s = null;

    News news = null;

    String content = null;

    try {

        s = HibernateUtil.getSession();

        s.beginTransaction();

        StringBuffer sb = new StringBuffer(“select * from news where id = ” + id);

        SQLQuery query = s.createSQLQuery(sb.toString());

        news = (News) query.addEntity(News.class).uniqueResult();

        content = ClobUtil.ClobToString(news.getContent());

        s.getTransaction().commit();

    } catch (Exception e) {

        logger.error(e.toString());

        HibernateUtil.endSession(s);

    } finally {

        HibernateUtil.endSession(s);

    }

    return content;

}

注意：要对获取到的实体类中的Clob类型数据转化为String类型  

5.Clob工具类：

public class ClobUtil {

    public static String ClobToString(Clob clob) {

        String clobStr = “”;

        Reader is = null;

        try {

            is = clob.getCharacterStream();

            // 得到流

            BufferedReader br = new BufferedReader(is);

            String s = null;

            s = br.readLine();

            StringBuffer sb = new StringBuffer();

            //执行循环将字符串全部取出赋值给StringBuffer，由StringBuffer转成String

            while (s != null) {

                sb.append(s);

                s = br.readLine();

            }

            clobStr = sb.toString();

        } catch (IOException e) {

            e.printStackTrace();

        } catch (SQLException e) {

            e.printStackTrace();

        }

        return clobStr;

    }

}

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