Hibernate对与Oracle中Clob类型的使用

Hibernate对与Oracle中Clob类型的使用

一.理解和分析：
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.建表：News新闻表

 

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;
	......
}

<?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="com.datanew.czfc.frontPage.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;
    }
    
}

  注意：通过流的方式读取Clob类型数据