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