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【第17章：Java数据库编程】_处理大数据对象（2）—处理BLOB数据

发布时间：2021-01-11 13:53:07编辑：雪饮阅读（）

 前文CLOB处理主要是用来处理大量文本的，而BLOB则是处理二进制内容的（文件）

在数据库中二进制内容存放字段类型为longblob，也同样和longtext一样最大可存储4G
向数据库中longblob字段存储一个图片
import java.sql.Connection ;
import java.sql.DriverManager ;
import java.sql.PreparedStatement ;
import java.io.File ;
import java.io.FileInputStream ;
import java.io.InputStream ;
public class Hello{
       public static final String DBDRIVER = "org.gjt.mm.mysql.Driver" ;
       public static final String DBURL = "jdbc:mysql://localhost:3306/xynes" ;
       public static final String DBUSER = "root" ;
       public static final String DBPASS = "" ;
       public static void main(String args[]) throws Exception{
              Class.forName(DBDRIVER) ;
            Connection conn = DriverManager.getConnection(DBURL,DBUSER,DBPASS) ;
             
              String sql = "INSERT INTO v9_admin(username,avatar) VALUES (?,?) " ;
              PreparedStatement pstmt = conn.prepareStatement(sql) ;
      
              File file = new File("d:" + File.separator + "kasumi.png") ;
              InputStream input = new FileInputStream(file);
             
              pstmt.setString(1,"kasumi") ;
              pstmt.setBinaryStream(2,input,(int)file.length());
              pstmt.executeUpdate() ;
              pstmt.close() ;
              conn.close() ;
       }
};

从数据库中longblob字段中取出一个图片
import java.sql.Connection ;
import java.sql.DriverManager ;
import java.sql.PreparedStatement ;
import java.io.File;
import java.io.InputStream ;
import java.io.FileOutputStream ;
import java.sql.ResultSet ;
import java.io.OutputStream ;
public class Hello{
       public static final String DBDRIVER = "org.gjt.mm.mysql.Driver" ;
       public static final String DBURL = "jdbc:mysql://localhost:3306/xynes" ;
       public static final String DBUSER = "root" ;
       public static final String DBPASS = "" ;
       public static void main(String args[]) throws Exception{
              Class.forName(DBDRIVER) ;
            Connection conn = DriverManager.getConnection(DBURL,DBUSER,DBPASS) ;
             
              String sql = "select username,avatar from v9_admin where userid=?" ;
              PreparedStatement pstmt = conn.prepareStatement(sql) ;
             
              pstmt.setInt(1,2) ;
              ResultSet rs=pstmt.executeQuery() ;
              if(rs.next()){
                     String username=rs.getString(1);
                    
                     InputStream input = rs.getBinaryStream(2);
                     File file = new File("d:" + File.separator + "kasumi.png");
                     OutputStream out = new FileOutputStream(file);
                    
                     int temp = 0 ;
                     while((temp=input.read())!=-1){
                            out.write(temp) ;
                     }
                     input.close() ;
                     out.close() ;
              }
              pstmt.close() ;
              conn.close() ;
       }
};
D:\>javac Hello.java
D:\>java Hello
从数据库中longblob字段中取出一个图片(使用Blob)
import java.sql.Connection ;
import java.sql.DriverManager ;
import java.sql.PreparedStatement ;
import java.io.File;
import java.io.FileOutputStream ;
import java.sql.ResultSet ;
import java.io.OutputStream ;
import java.sql.Blob ;
public class Hello{
       public static final String DBDRIVER = "org.gjt.mm.mysql.Driver" ;
       public static final String DBURL = "jdbc:mysql://localhost:3306/xynes" ;
       public static final String DBUSER = "root" ;
       public static final String DBPASS = "" ;
       public static void main(String args[]) throws Exception{
              Class.forName(DBDRIVER) ;
            Connection conn = DriverManager.getConnection(DBURL,DBUSER,DBPASS) ;
             
              String sql = "select username,avatar from v9_admin where userid=?" ;
              PreparedStatement pstmt = conn.prepareStatement(sql) ;
             
              pstmt.setInt(1,2) ;
              ResultSet rs=pstmt.executeQuery() ;
              if(rs.next()){
                     String username=rs.getString(1);
                    
                     Blob b = rs.getBlob(2) ;
                     File file = new File("d:" + File.separator + "kasumi.png");
                     OutputStream out = new FileOutputStream(file);
                     out.write(b.getBytes(1,(int)b.length())) ;
                     out.close() ;
              }
              pstmt.close() ;
              conn.close() ;
       }
};
D:\>javac Hello.java
D:\>java Hello