项目代码如下：
config配置文件：
className=com.mysql.jdbc.Driver url=jdbc:mysql://localhost:3306/lob user=root password=root
com.itheima.util包下DBUtil.java
package com.itheima.util;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
public class DBUtil {
private static Properties properties = null;
static {
properties = new Properties();
try {
properties.load(new FileReader(DBUtil.class.getClassLoader().getResource("config.properties").getPath()));
} catch (FileNotFoundException e) {
e.printStackTrace();
throw new RuntimeException(e);
} catch (IOException e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
public static Connection getConn() {
String className = properties.getProperty("className");
String url = properties.getProperty("url");
String user = properties.getProperty("user");
String password = properties.getProperty("password");
Connection conn;
try {
Class.forName(className);
conn = DriverManager.getConnection(url, user, password);
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException(e);
} catch (ClassNotFoundException e) {
e.printStackTrace();
throw new RuntimeException(e);
}
return conn;
}
public static void close (Connection conn, PreparedStatement ps, ResultSet rs) {
if(rs != null) {
try {
rs.close();
} catch (SQLException e) {
rs = null;
}
}
if(ps != null) {
try {
ps.close();
} catch (SQLException e) {
ps = null;
}
}
if(conn != null) {
try {
conn.close();
} catch (SQLException e) {
conn = null;
}
}
}
}
com.itheima.lob包下TextDemo.java（实现存储大文本数据）
package com.itheima.lob;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.junit.Test;
import com.itheima.util.DBUtil;
public class TextDemo {
/*
create table textdemo (
id int primary key auto_increment,
name varchar(50),
content mediumtext
);
*/
@Test
public void getText(){
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
String sql = "select * from textdemo";
try {
conn = DBUtil.getConn();
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while(rs.next()) {
String name = rs.getString(2);
Reader reader = rs.getCharacterStream(3);
Writer writer = new FileWriter(name);
int len = 0;
char []data = new char[1024];
while((len = reader.read(data)) != -1) {
writer.write(data, 0, len);
}
}
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException(e);
} catch (IOException e) {
e.printStackTrace();
throw new RuntimeException(e);
} finally {
DBUtil.close(conn, ps, rs);
}
}
@Test
public void addText() {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
String sql = "insert into textdemo values(null,?,?)";
try {
conn = DBUtil.getConn();
ps = conn.prepareStatement(sql);
ps.setString(1, "钢铁是怎样炼成.txt");
File file = new File("1.txt");
ps.setCharacterStream(2, new FileReader(file), (int)file.length());
ps.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException(e);
} catch (FileNotFoundException e) {
e.printStackTrace();
throw new RuntimeException(e);
} finally {
DBUtil.close(conn, ps, rs);
}
}
}
com.itheima.lob包下BlobDemo.java（实现存储大二进制数据）
package com.itheima.lob;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.junit.Test;
import com.itheima.util.DBUtil;
/*
create table blobdemo(
id int primary key auto_increment,
name varchar(50),
content blob
);
*/
public class BlobDemo {
@Test
public void getBlob() {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
String sql = "select * from blobdemo";
try {
conn = DBUtil.getConn();
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while(rs.next()) {
String name = rs.getString(2);
InputStream is = rs.getBlob(3).getBinaryStream();
OutputStream os = new FileOutputStream(name);
int len = 0;
byte[] data = new byte[1024];
while((len = is.read(data)) != -1) {
os.write(data, 0, len);
}
}
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException(e);
} catch (IOException e) {
e.printStackTrace();
throw new RuntimeException(e);
} finally {
DBUtil.close(conn, ps, rs);
}
}
@Test
public void addBlob() {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
String sql = "insert into blobdemo values (null,?,?)";
try {
conn = DBUtil.getConn();
ps = conn.prepareStatement(sql);
ps.setString(1, "洛天依.mp3");
File file = new File("1.mp3");
ps.setBinaryStream(2, new FileInputStream(file), (int)file.length());
ps.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException(e);
} catch (FileNotFoundException e) {
e.printStackTrace();
throw new RuntimeException(e);
} finally {
DBUtil.close(conn, ps, rs);
}
}
}
需要注意的是：
ps.setCharacterStream(2, new FileReader(file), (int)file.length());有三种重载形式
ps.setBinaryStream(2, new FileInputStream(file), (int)file.length());有三种重载形式
这两个方法只有第二种重载形式mysql的jar包里实现了，其余两种没实现，故为抽象方法，所以如果使用这两种方法会提示抽象方法错误
还有就是如果上传时，提示java.lang.OutOfMemoryError，则说明超出虚拟机内存，这是可以点击
-Xms64m设置虚拟机最小内存为64M
-Xmx256m设置虚拟机最大内存为256M
注：jdk5.0以前虚拟机默认的最大内存为64M
如果提示com.mysql.jdbc.PacketTooBigException,说明程序和数据库之间传送的数据包超过了默认数据包的大小，这时通过可以修改mysql目录下的配置文件my.ini解决。
只需要在【mysqld】标签下添加一行max_allowed_packet属性值就可以了
[mysqld] max_allowed_packet=64M
时间： 2024-10-10 02:36:19