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Hibernate Gossip: Blob、Clob - Oracle 9i

在MySQL中对Blob与Clob是比较简单的，如果在Oracle DB中则复杂一些，首先您要先了解 JDBC在Oracle 9i中的作法。

由于Oracle JDBC不允许使用批次方式进行操作，所以您要在Hibernate设定档中，将hibernate.jdbc.batch_size设定为0，例如：

hibernate.cfg.xml

<?xml version="1.0" encoding="utf-8"?> 
<!DOCTYPE hibernate-configuration PUBLIC
	"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
	
<hibernate-configuration> 

    <session-factory> 

        ....
                                                                                                                                                                                                                                                                                                                                                        <property name="hibernate.jdbc.batch_size">0</property> 

        <mapping resource="onlyfun/caterpillar/File.hbm.xml"/> 
        
    </session-factory> 

</hibernate-configuration>

假设您的表格使用以下的SQL建立：

CREATE TABLE t_file (
          id INTEGER NOT NULL,
          des CLOB,
          image BLOB
      );

假设FILE类别设定如下：

FILE.java

package onlyfun.caterpillar;

import java.sql.Blob;
import java.sql.Clob;

public class File {
    private Integer id;
    private Clob des;
    private Blob image;

    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }	
    public Clob getDes() {
        return des;
    }
    public void setDes(Clob des) {
        this.des = des;
    }
    public Blob getImage() {
        return image;
    }
    public void setImage(Blob image) {
        this.image = image;
    }
}

映像档案设定如下：

FILE.hbm.xml

<?xml version="1.0" encoding="utf-8"?> 
<!DOCTYPE hibernate-mapping 
    PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 

<hibernate-mapping> 
    <class name="onlyfun.caterpillar.File" table="t_file"> 

        <id name="id" column="id"> 
            <generator class="native"/> 
        </id> 

        <property name="des" column="des"/> 
        <property name="image" column="image"/> 
    </class> 

</hibernate-mapping>

接下来Hibernate在存取Blob/Clob时，主要要模拟JDBC在Oracle中的方式，以下是个简单的储存Blob/Clob的方式：

BlobClobDemo.java

package onlyfun.caterpillar;

import java.io.FileInputStream;
import java.io.IOException;
import java.sql.SQLException;

import org.hibernate.Hibernate;
import org.hibernate.LockMode;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class BlobClobDemo {
    public static void main(String[] args) throws IOException, SQLException {
        // Configuration 负责管理 Hibernate 配置讯息
        Configuration config = new Configuration().configure();
        // 根据 config 建立 SessionFactory
        // SessionFactory 将用于建立 Session
        SessionFactory sessionFactory = config.buildSessionFactory(); 
		
        File file = new File();
        // 先建立空的字段
        file.setDes(Hibernate.createClob(" "));
        file.setImage(Hibernate.createBlob(new byte[1]));

        Session session = sessionFactory.openSession();
        Transaction tx = session.beginTransaction();
        session.save(file);

        // 执行flush，让Hibernate INSERT 空字段
        session.flush();
        // 执行refresh，让Hibernate执行SELECT FOR UPDATE
        session.refresh(file, LockMode.UPGRADE);
		
        FileInputStream fileInputStream = new FileInputStream("c:\\workspace\\Wind.bmp");
	
        // 重新设定真正要写入的Blob/Clob数据
        file.setDes(Hibernate.createClob("...blah...blah..."));
        file.setImage(Hibernate.createBlob(fileInputStream));

        // 再次save
        session.save(file);
		
        tx.commit();
        session.close();
        fileInputStream.close();

        sessionFactory.close();

    }
}

更多其它在Oracle中的解决方案，您可以参考 Using Clobs/Blobs with Oracle and Hibernate