jdbc基础 (三) 大文本、二进制数据处理

LOB (Large Objects)   分为：CLOB和BLOB，即大文本和大二进制数据

CLOB：用于存储大文本

BLOB：用于存储二进制数据，例如图像、声音、二进制文件

在mysql中,只有BLOB,没有CLOB，mysql存储大文本用TEXT

TEXT  分为：TINYTEXT、TEXT、MEDIUMTEXT和LONGTEXT

BLOB 分为：TINYBLOB、BLOB、MEDIUMBLOB和LONGBLOB

取值范围如下图：

下面来看具体的代码实现：

package com.cream.ice.jdbc;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
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;

/**
 * 大文本数据操作
 * 
 * 假设数据库中已存在表test: 
 * create table test(
 *        id int primary key,
 *        content longtext
 * );
 * 
 * @author ice
 *
 */
public class ClobDemo {
    
    Connection connection = null;
    PreparedStatement statement = null;
    ResultSet resultSet=null;
    
    @Test
    public void add(){
        try {
            connection=JdbcUtils.getConnection();
            statement=connection.prepareStatement("insert into test (id,content) values (?,?)");
            statement.setInt(1, 1);
            
            //大文本要使用流的形式。将d:/test.txt内容添加至该记录的content字段
            File file = new File("d:/test.txt");
            Reader reader = new FileReader(file);
            //不能使用long的参数，因为mysql根本支持不到那么大的数据，所以没有实现
            statement.setCharacterStream(2, reader, (int)file.length());
            
            int i = statement.executeUpdate();
            if(i>0)
                System.out.println("插入成功");
            
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } finally{
            JdbcUtils.releaseResources(null, statement, connection);
        }
    }
    
    @Test
    public void read(){
        try {
            connection = JdbcUtils.getConnection();
            statement = connection.prepareStatement("select * from test where id=?");
            statement.setInt(1, 1);

            //将读取内容保存到E盘上
            resultSet = statement.executeQuery();
            while(resultSet.next()){
                Reader reader = resultSet.getCharacterStream("content");
                Writer writer = new FileWriter("e:/test.txt");
                char buffer[] = new char[1024];
                int len = -1;
                while((len=reader.read(buffer))!=-1){
                    writer.write(buffer, 0, len);
                }
                reader.close();
                writer.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JdbcUtils.releaseResources(resultSet, statement, connection);
        }
    }
}

package com.cream.ice.jdbc;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import org.junit.Test;

/**
 * 大二进制数据操作
 * 
 * 假设数据库中已存在表test: 
 * create table test(
 *        id int primary key,
 *        content longblob
 * );
 * 
 * @author ice
 *
 */
public class BlobDemo {
    Connection connection = null;
    PreparedStatement statement = null;
    ResultSet resultSet=null;
    
    @Test
    public void add(){
        try {
            connection=JdbcUtils.getConnection();
            statement=connection.prepareStatement("insert into test (id,content) values (?,?)");
            statement.setInt(1, 1);
            
            InputStream in = new FileInputStream("d:/test.jpg");
            statement.setBinaryStream(2, in, in.available());
            
            int i = statement.executeUpdate();
            if(i>0)
                System.out.println("插入成功");
            
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JdbcUtils.releaseResources(null, statement, connection);
        }
    }
    
    @Test
    public void read(){
        try {
            connection = JdbcUtils.getConnection();
            statement = connection.prepareStatement("select * from test where id=?");
            statement.setInt(1, 1);

            //保存到E盘上
            resultSet = statement.executeQuery();
            while(resultSet.next()){
                InputStream in = resultSet.getBinaryStream("content");
                OutputStream out = new FileOutputStream("e:/test.jpg");
                byte b[] = new byte[1024];
                int len = -1;
                while((len=in.read(b))!=-1){
                    out.write(b, 0, len);
                }
                out.close();
                in.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JdbcUtils.releaseResources(resultSet, statement, connection);
        }
    }
}

这里使用了我上一篇jdbc基础中的JdbcUtils工具类，同时也使用了单元测试来测试两个成员方法，代码已亲测可运行。

csdn博文地址：jdbc基础 (三)  大文本、二进制数据处理