关于clob的问题,请教大家!拜托了!急 在struts+spring+hibernate模式下,如何对oracle9i里的一个clob类型的表字段进行读写操作?(希望教我能细到如何定义,因为我对clob一窍不通)还有我用的数据库的驱动是ojdbc14.jar 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 Oracle的Blob字段比较特殊,他比long字段的性能要好很多,可以用来保存例如图片之类的二进制数据。 写入Blob字段和写入其它类型字段的方式非常不同,因为Blob自身有一个cursor,你必须使用cursor对blob进行操作,因而你在写入Blob之前,必须获得cursor才能进行写入,那么如何获得Blob的cursor呢? 这需要你先插入一个empty的blob,这将创建一个blob的cursor,然后你再把这个empty的blob的cursor用select查询出来,这样通过两步操作,你就获得了blob的cursor,可以真正的写入blob数据了。 看下面的JDBC的demo,把oraclejdbc.jar这个二进制文件写入数据库表javatest的content字段(这是一个blob型字段)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()]; 另一种实现方法,节省内存 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()); }}} 仔细看上例,分三步: 1、插入空blobinto javatest(name,content) values(?,empty_blob()); 2、获得blob的cursorselect content from javatest where name= ? for update; 注意!!!必须加for update,这将锁定该行,直至该行被修改完毕,保证不产生并发冲突。 3、update javatest set content=? where name= 用cursor往数据库写数据 这里面还有一点要提醒大家: JDK1.3带的JDBC2.0规范是不完善的,只有读Blob的接口,而没有写Blob的接口,JDK1.4带的JDBC3.0加入了写Blob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.Bloboracle.sql.BLOB 注意看blob的大小写,是不一样的。写程序的时候不要搞混了。 下面看看用Hibernate怎么写,原理是一样的,也要分三步,但是代码简单很多 这是Cat对象定义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;}}这是Cat.hbm.xml<?xml version="1.0"?><!DOCTYPE hibernate-mapping SYSTEM "http://hibernate.sourceforge.net/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写入Blob的例子,相比JDBC,已经简单轻松多了,也不用写那些Oracle特殊的sql了: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) {} } }} 最近我用Oracle9i2做clob,blob时发现clob在字符长度1000左右有个盲区,操作会出现失败,如果碰到这个问题请过滤一次。升级oracle驱动无效,这个就不用考虑了……顺便up…… 谢谢大家,问题已经解决了,用oracle最新的驱动,可以像操作varchar2一样操作clob,现在结帖 Spring + Ibatis + c3p0 数据库连接数问题。急。。。 界面问题请教,新手初学,望指教,谢谢 一个垃圾回收的问题 JTable如何实现undo?请大家帮忙. 继承的树怎么显示不出来? Class.forName(String str),str是什么编码格式? java程序如何调用在不同文件夹下的class java里面怎样找到局域网内所有机器的ip地址! (急)请问高手: JTextArea 限制用户输入问题!(急!急!急!) 对象流的写入和读出问题? jtable 的简单使用,如何增加删除行
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()]; 另一种实现方法,节省内存
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());
}
}}
仔细看上例,分三步: 1、插入空blobinto javatest(name,content) values(?,empty_blob()); 2、获得blob的cursorselect content from javatest where name= ? for update; 注意!!!必须加for update,这将锁定该行,直至该行被修改完毕,保证不产生并发冲突。 3、update javatest set content=? where name= 用cursor往数据库写数据 这里面还有一点要提醒大家: JDK1.3带的JDBC2.0规范是不完善的,只有读Blob的接口,而没有写Blob的接口,JDK1.4带的JDBC3.0加入了写Blob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.Bloboracle.sql.BLOB 注意看blob的大小写,是不一样的。写程序的时候不要搞混了。 下面看看用Hibernate怎么写,原理是一样的,也要分三步,但是代码简单很多 这是Cat对象定义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;}
}
这是Cat.hbm.xml<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping SYSTEM "http://hibernate.sourceforge.net/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写入Blob的例子,相比JDBC,已经简单轻松多了,也不用写那些Oracle特殊的sql了: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) {}
}
}
}