JDBC之处理大数据类型

这次以MySQL与Oralce为例。

 

先看表结构把：

 ------------------------处理大数对象-----------------

 ------------------------MySQL----------------------
 --有4种text类型：tinytext、text、mediumtext和longtext
 create table t_clob
 (
     id      integer ,
     resume  longtext,
     primary key(id)
 );

 --有4种blob类型：tinyblob、blob、mediumblob和longblob
 create table t_blob
 (
     id      integer ,
     photo   longblob,
     primary key(id)
 );


 -----------------------Oracle------------------------
 --clob
 create table t_clob
 (
     id      integer ,
     resume  clob,
     primary key(id)
 );

 --blob
 create table t_blob
 (
     id      integer ,
     photo   blob,
     primary key(id)
 );

 

 

先考虑Clob类型的，下面的代码适用于MySQL与Oralce

 

 package org.monday.demo;

 import java.io.File;
 import java.io.FileReader;
 import java.io.PrintWriter;
 import java.io.Reader;
 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;

 import org.junit.Test;
 import org.monday.util.JdbcUtil;

 /**
  * Clob大文本数据操作
  */
 public class ClobMain {

     private static String INSERT_CLOB = "insert into t_clob(id,resume)values(?,?)";
     private static String SELECT_CLOB = "select * from t_clob where id=?";

     @Test
     public void insert() {
         Connection conn = null;
         PreparedStatement pstmt = null;
         try {
             File file = new File("src/电子商务.txt");
             Reader reader = new FileReader(file);
             conn = JdbcUtil.getConnection();
             pstmt = conn.prepareStatement(INSERT_CLOB);
             pstmt.setInt(1, 1);
             pstmt.setCharacterStream(2, reader, (int) file.length());
             pstmt.executeUpdate();
         } catch (Exception e) {
             throw new RuntimeException(e);
         } finally {
             JdbcUtil.release(conn, pstmt, null);
         }
     }

     @Test
     public void read() {
         Connection conn = null;
         PreparedStatement pstmt = null;
         ResultSet rs = null;
         try {
             conn = JdbcUtil.getConnection();
             pstmt = conn.prepareStatement(SELECT_CLOB);
             pstmt.setInt(1, 1);
             rs = pstmt.executeQuery();
             if (rs.next()) {
                 Reader reader = rs.getCharacterStream("resume");
                 PrintWriter out = new PrintWriter(System.out); // 打印到控制台
                 // PrintWriter out= new PrintWriter("src/out.txt"); // 打印到文本
                 try {
                     int len = 0;
                     char[] buffer = new char[1024];
                     while ((len = reader.read(buffer)) > 0) {
                         out.write(buffer, 0, len);
                     }
                 } finally {
                     if (reader != null) {
                         reader.close();
                     }
                     out.close();
                 }
             }
         } catch (Exception e) {
             throw new RuntimeException(e);
         } finally {
             JdbcUtil.release(conn, pstmt, rs);
         }
     }
 }

 

 

接下来是Blob类型，这个MySQL与Oracle还是有些不一样的。看仔细了。。

 

 package org.monday.demo;

 import java.io.File;
 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;
 import org.monday.util.JdbcUtil;

 /**
  * Blob图片数据操作
  * MySQL与Oralce有所不同
  */
 public class BlobMain {

     private static String INSERT_BLOB = "insert into t_blob(id,photo)values(?,?)";
     private static String SELECT_BLOB = "select * from t_blob where id=?";

     @Test
     public void insert() {
         Connection conn = null;
         PreparedStatement pstmt = null;
         try {
             File file = new File("src/王若琳.jpg");
             InputStream in = new FileInputStream(file);
             conn = JdbcUtil.getConnection();
             pstmt = conn.prepareStatement(INSERT_BLOB);
             pstmt.setInt(1, 1);
             pstmt.setAsciiStream(2, in, (int) file.length());
             pstmt.executeUpdate();
         } catch (Exception e) {
             throw new RuntimeException(e);
         } finally {
             JdbcUtil.release(conn, pstmt, null);
         }
     }

     @Test
     public void read() {
         Connection conn = null;
         PreparedStatement pstmt = null;
         ResultSet rs = null;
         try {
             conn = JdbcUtil.getConnection();
             pstmt = conn.prepareStatement(SELECT_BLOB);
             pstmt.setInt(1, 1);
             rs = pstmt.executeQuery();
             if (rs.next()) {
                 InputStream in = rs.getBlob("photo").getBinaryStream();
                 // 或者InputStream in = rs.getAsciiStream("photo"); 但是这个却Oralce不好用
                 OutputStream out = new FileOutputStream("src/out.jpg");
                 try {
                     int len = 0;
                     byte[] b = new byte[1024];
                     while ((len = in.read(b)) > 0) {
                         out.write(b, 0, len);
                     }
                 } finally {
                     if (in != null) {
                         in.close();
                     }
                     if (out != null) {
                         out.close();
                     }
                 }
             }
         } catch (Exception e) {
             throw new RuntimeException(e);
         } finally {
             JdbcUtil.release(conn, pstmt, rs);
         }
     }


     /**
      * Oralce插入Blob类型很特殊
      */
     @Test
     public void insert_oralce() {

         // 插入Oralce用的
         String INSERT_BLOB_ORACLE = "insert into t_blob(id,photo)values(?,empty_blob())"; // empty_blob()固定的
         String SELECT_BLOB_ORACLE = "select * from t_blob where id=? for update"; // for update 固定的，不可去

         Connection conn = null;
         PreparedStatement pstmt = null;
         ResultSet rs = null;
         try {
             // 不用开启事务，网上传说要开启事务
             // conn.setAutoCommit(false);
             conn = JdbcUtil.getConnection();
             // 插入一个指针
             pstmt = conn.prepareStatement(INSERT_BLOB_ORACLE);
             pstmt.setInt(1, 1);
             pstmt.executeUpdate();

             // 读取插入的那个指针
             pstmt = conn.prepareStatement(SELECT_BLOB_ORACLE);
             pstmt.setInt(1, 1);
             rs = pstmt.executeQuery();
             if (rs.next()) {
                 InputStream in = new FileInputStream(new File("src/王若琳.jpg"));
                 // 得到java.sql.Blob对象后强制转换为oracle.sql.BLOB
                 oracle.sql.BLOB blob = (oracle.sql.BLOB) rs.getBlob("photo");
                 OutputStream out = blob.getBinaryOutputStream();
                 try {
                     byte[] b = new byte[blob.getBufferSize()];
                     int len;
                     while ((len = in.read(b)) > 0) {
                         out.write(b, 0, len);
                     }
                 } finally {
                     if (in != null) {
                         in.close();
                     }
                     if (out != null) {
                         out.close();
                     }
                 }
             }
         } catch (Exception e) {
             throw new RuntimeException(e);
         } finally {
             JdbcUtil.release(conn, pstmt, rs);
         }
     }
 }