java servlet 读写mysql中存储的二进制文件

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数据准备

CREATE TABLE stuinfo (id INT (11) NOT NULL auto_increment,NAME VARCHAR (10) DEFAULT NULL,content LONGTEXT,image LONGBLOB,PRIMARY KEY (id)) ENGINE = INNODB;

servlet 及本地方法

需要mysql驱动包及servlet-api.jar

访问地址：http://localhost:8080/xxx/download

package test;import java.io.BufferedInputStream;import java.io.BufferedOutputStream;import java.io.BufferedReader;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.InputStreamReader;import java.io.OutputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;@WebServlet(name = "download", urlPatterns = { "/download" })public class TestFile extends HttpServlet {//servlet 的例子@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 驱动程序名        String driver = "com.mysql.jdbc.Driver";        // URL指向要访问的数据库名scutcs        String url = "jdbc:mysql://127.0.0.1:3306/antdb";        // MySQL配置时的用户名        String user = "root";         // MySQL配置时的密码        String password = "123456";                 //transaction dealing        PreparedStatement pstam=null;        String sql="select * from stuinfo where name=?";        try {        // 加载驱动程序            Class.forName(driver);            // 连续数据库            Connection conn = DriverManager.getConnection(url, user, password);            pstam=conn.prepareStatement(sql);            pstam.setString(1, "cjc");            ResultSet reset=pstam.executeQuery();            while(reset.next()){                BufferedReader br=new BufferedReader(reset.getCharacterStream(3));                String str=null;                while((str=br.readLine())!=null){                    System.out.println(str);                }                BufferedInputStream bis=new BufferedInputStream(reset.getBinaryStream(4));                // 写明要下载的文件的大小                  //resp.setContentLength((int) file.length());                  resp.setHeader("Content-Disposition", "attachment;filename="                          + "ookkkk.jpg");// 设置在下载框默认显示的文件名                  resp.setContentType("application/octet-stream");// 指明response的返回对象是文件流                  // 读出文件到response                  // 这里是先需要把要把文件内容先读到缓冲区                  // 再把缓冲区的内容写到response的输出流供用户下载                  //FileInputStream fileInputStream = new FileInputStream(file);                  //BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream);                  byte[] b = new byte[bis.available()];                  bis.read(b);                  OutputStream outputStream = resp.getOutputStream();                  outputStream.write(b);                  // 人走带门                  bis.close();                  outputStream.flush();                  outputStream.close();                                  reset.close();                pstam.close();                conn.close();            }        } catch (SQLException e) {            e.printStackTrace();        } catch (FileNotFoundException e){            e.printStackTrace();        } catch (IOException e){            e.printStackTrace();        } catch (Exception e){            e.printStackTrace();        }}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}public static void main(String[] args) throws Exception {readd();}//本地存储文件 图片到服务器的例子public static void writer() throws Exception {// 驱动程序名        String driver = "com.mysql.jdbc.Driver";        // URL指向要访问的数据库名scutcs        String url = "jdbc:mysql://127.0.0.1:3306/antdb";        // MySQL配置时的用户名        String user = "root";         // MySQL配置时的密码        String password = "123456";// 加载驱动程序        Class.forName(driver);        // 连续数据库        Connection conn = DriverManager.getConnection(url, user, password);                 //transaction dealing        PreparedStatement pstam=null;        String sql="insert into stuinfo(name,content,image) values(?,?,?);";        try {            pstam=conn.prepareStatement(sql);            pstam.setString(1, "cjc");                         File file=new File("D:/安装前必看.txt");            InputStream itxt=new FileInputStream(file);            BufferedReader br=new BufferedReader(new InputStreamReader(itxt));            pstam.setCharacterStream(2,br,(int)file.length());                         File file1=new File("D:/18285693_231156450339_2.jpg");            InputStream isimg=new FileInputStream(file1);            pstam.setBinaryStream(3, isimg, (int)file1.length());                         pstam.executeUpdate();                         br.close();            itxt.close();            isimg.close();            pstam.close();            conn.close();        } catch (SQLException e) {            e.printStackTrace();        } catch (FileNotFoundException e){            e.printStackTrace();        } catch (IOException e){            e.printStackTrace();        }    }//本地读取 文件图片的例子public static void readd() throws Exception {// 驱动程序名        String driver = "com.mysql.jdbc.Driver";        // URL指向要访问的数据库名scutcs        String url = "jdbc:mysql://127.0.0.1:3306/antdb";        // MySQL配置时的用户名        String user = "root";         // MySQL配置时的密码        String password = "123456";// 加载驱动程序        Class.forName(driver);        // 连续数据库        Connection conn = DriverManager.getConnection(url, user, password);                 //transaction dealing        PreparedStatement pstam=null;        String sql="select * from stuinfo where name=?;";        try {            pstam=conn.prepareStatement(sql);            pstam.setString(1, "cjc");            ResultSet reset=pstam.executeQuery();            while(reset.next()){                System.out.println("Read text document...");                BufferedReader br=new BufferedReader(reset.getCharacterStream(3));                String str=null;                while((str=br.readLine())!=null){                    System.out.println(str);                }                System.out.println("Read text document OK!");                                 System.out.println("Read image file...");                BufferedOutputStream bos=new BufferedOutputStream(new FileOutputStream(new File("D://result.jpg")));                byte[] buf=new byte[1024];                BufferedInputStream bis=new BufferedInputStream(reset.getBinaryStream(4));                int count=-1;                while((count=bis.read(buf, 0, 1024))!=-1){                    bos.write(buf, 0, count);                }                bos.flush();                System.out.println("Read image file OK!");                bos.close();            }            reset.close();            pstam.close();            conn.close();        } catch (SQLException e) {            e.printStackTrace();        } catch (FileNotFoundException e){            e.printStackTrace();        } catch (IOException e){            e.printStackTrace();        }    }}

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