使用JDBC和Hibernate來寫入Blob型數(shù)據(jù)到Oracle中 閱讀次數(shù)4291
出處 不詳
Oracle的Blob字段比較特殊，他比long字段的性能要好很多,，可以用來保存例如圖片之類的二進(jìn)制數(shù)據(jù),。
寫入Blob字段和寫入其它類型字段的方式非常不同，因?yàn)锽lob自身有一個(gè)cursor,，你必須使用cursor對blob進(jìn)行操作,，因而你在寫入Blob之前，必須獲得cursor才能進(jìn)行寫入,，那么如何獲得Blob的cursor呢,？
這需要你先插入一個(gè)empty的blob，這將創(chuàng)建一個(gè)blob的cursor,，然后你再把這個(gè)empty的blob的cursor用select查詢出來,，這樣通過兩步操作，你就獲得了blob的cursor,，可以真正的寫入blob數(shù)據(jù)了,。
看下面的JDBC的demo，把oraclejdbc.jar這個(gè)二進(jìn)制文件寫入數(shù)據(jù)庫表javatest的content字段(這是一個(gè)blob型字段)
代碼:
import java.sql.*;
import java.io.*;
import oracle.sql.*;
public class WriteBlob {
public static void main(String[] args) {
try {
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl","fankai","fankai");
conn.setAutoCommit(false);
BLOB blob = null;
PreparedStatement pstmt = conn.prepareStatement("insert into javatest(name,content) values(?,empty_blob())");
pstmt.setString(1,"fankai");
pstmt.executeUpdate();
pstmt.close();
pstmt = conn.prepareStatement("select content from javatest where name= ? for update");
pstmt.setString(1,"fankai");
ResultSet rset = pstmt.executeQuery();
if (rset.next()) blob = (BLOB) rset.getBlob(1);
String fileName = "oraclejdbc.jar";
File f = new File(fileName);
FileInputStream fin = new FileInputStream(f);
System.out.println("file size = " + fin.available());
pstmt = conn.prepareStatement("update javatest set content=? where name=?");
OutputStream out = blob.getBinaryOutputStream();
int count = -1, total = 0;
byte[] data = new byte[(int)fin.available()];
fin.read(data);
out.write(data);
/*
byte[] data = new byte[blob.getBufferSize()]; 另一種實(shí)現(xiàn)方法,節(jié)省內(nèi)存
while ((count = fin.read(data)) != -1) {
total += count;
out.write(data, 0, count);
}
*/
fin.close();
out.close();
pstmt.setBlob(1,blob);
pstmt.setString(2,"fankai");
pstmt.executeUpdate();
pstmt.close();
conn.commit();
conn.close();
} catch (SQLException e) {
System.err.println(e.getMessage());
e.printStackTrace();
} catch (IOException e) {
System.err.println(e.getMessage());
}
}
}
仔細(xì)看上例,，分三步：
1,、插入空blob
into javatest(name,content) values(?,empty_blob());
2、獲得blob的cursor
select content from javatest where name= ? for update;
注意?。,。”仨毤觙or update,，這將鎖定該行,，直至該行被修改完畢，保證不產(chǎn)生并發(fā)沖突,。
3,、update javatest set content=? where name=
用cursor往數(shù)據(jù)庫寫數(shù)據(jù)
這里面還有一點(diǎn)要提醒大家：
JDK1.3帶的JDBC2.0規(guī)范是不完善的，只有讀Blob的接口,，而沒有寫B(tài)lob的接口,，JDK1.4帶的JDBC3.0加入了寫B(tài)lob的接口。你可以使用JDBC3.0的接口,，也可以直接使用Oracle的JDBC的API,，我在上例中使用了Oracle的JDBC的API。
另外要注意的是：
java.sql.Blob
oracle.sql.BLOB
注意看blob的大小寫，是不一樣的,。寫程序的時(shí)候不要搞混了,。
下面看看用Hibernate怎么寫，原理是一樣的,，也要分三步,，但是代碼簡單很多
這是Cat對象定義
代碼:
package com.fankai;
import java.sql.Blob;
public class Cat {
private String id;
private String name;
private char sex;
private float weight;
private Blob image;
public Cat() { }
public String getId() { return id; }
public void setId(String id) { this.id = id; }
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public char getSex() { return sex; }
public void setSex(char sex) { this.sex = sex; }
public float getWeight() { return weight; }
public void setWeight(float weight) { this.weight = weight; }
public Blob getImage() { return image; }
public void setImage(Blob image) { this.image = image;}
}
這是Cat.hbm.xml
代碼:
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping SYSTEM "http://hibernate./hibernate-mapping-2.0.dtd">
<hibernate-mapping>
<class name="com.fankai.Cat" table="cat">
<!--jcs-cache usage="read-only"/-->
<id name="id" unsaved-value="null">
<generator class="uuid.hex"/>
</id>
<property name="name" length="16" not-null="true"/>
<property name="sex" length="1" not-null="true"/>
<property name="weight" />
<property name="image" />
</class>
</hibernate-mapping>
下面是完整的用Hibernate寫入Blob的例子,，相比JDBC,，已經(jīng)簡單輕松多了，也不用寫那些Oracle特殊的sql了：
代碼:
package com.fankai;
import java.sql.Blob;
import net.sf.hibernate.*;
import oracle.sql.*;
import java.io.*;
public class TestCatHibernate {
public static void testBlob() {
Session s = null;
byte[] buffer = new byte[1];
buffer[0] = 1;
try {
SessionFactory sf = HibernateSessionFactory.getSessionFactory();
s = sf.openSession();
Transaction tx = s.beginTransaction();
Cat c = new Cat();
c.setName("Robbin");
c.setImage(Hibernate.createBlob(buffer));
s.save(c);
s.flush();
s.refresh(c, LockMode.UPGRADE);
BLOB blob = (BLOB) c.getImage();
OutputStream out = blob.getBinaryOutputStream();
String fileName = "oraclejdbc.jar";
File f = new File(fileName);
FileInputStream fin = new FileInputStream(f);
int count = -1, total = 0;
byte[] data = new byte[(int)fin.available()];
fin.read(data);
out.write(data);
fin.close();
out.close();
s.flush();
tx.commit();
} catch (Exception e) {
System.out.println(e.getMessage());
} finally {
if (s != null)
try {
s.close();
} catch (Exception e) {}
}
}
}
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