Java中将图片保存到数据库中

时间 2021-07-14 标签 stylesheet java string sqlserver initialization 数据库

在实际的开发中，我们可能需要将图片、影音等文件直接保存到数据库中，然后通过编程方式将数据读出进行使用。例如将读出的图片数据显示出来，将读出的电影文件播放出来。

二进制数据直接保存到文件和从文件中读出非常的简单。和普通的数据库操作差别不大。只是用到部分流操作。例如各种输入输出流操作。所以深刻理解流操是非常重要的。

在此我借助于一个JSP的简单实例进行讲解。此实例保存职员数据，其中职员数据包含一个图片列。此列保存每名员工的照片。在此将照片直接保存到数据库中。首先建立职员信息表EmployeeInfo，表列非常的简单

employeeId:职员编号（自动增长）；employeeName:职员姓名；age:职员年龄；pic:职员图片（image类型）

首先讲解信息的保存。先建立一个录入界面index.jsp，其中包含一个<input type="file"/>元素，用于让用户选择图片文件。

页面代码如下（不做过多讲解）：

<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <base href="<%=basePath%>">

    <title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

</head>

<body>
    <form action="addServlet" method="POST">
    <table border="15" width="60%" align="center">
      <tr>
       <td width="30%" align="right">EmployeeName:</td>
       <td width="70%" align="left"><input type="text" name="employeeName"/></td>
      </tr>
      <tr>
       <td width="30%" align="right">Age:</td>
       <td width="70%" align="left"><input type="text" name="age"/></td>
      </tr>
      <tr>
       <td width="30%" align="right">Image:</td>
       <td width="70%" align="left"><input type="file" name="pic"/></td>
      </tr>
      <tr>
       <td colspan="2" align="center"><input type="submit" value="add"/></td>
      </tr>
    </table>
    </form>
</body>
</html>

页面请求addServlet，获取录入信息，并调用JavaBean实现数据保存。Servlet代码如下：

package com.frank.action;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.frank.rule.*;
public class AddServlet extends HttpServlet {

/**
* Constructor of the object.
*/
public AddServlet() {
super();
}

/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}

  String employeeName=request.getParameter("employeeName");
  int age=Integer.parseInt(request.getParameter("age"));
  String pic=request.getParameter("pic");
  EmployeeDAO employeeDAO=new EmployeeDAO();
  if(employeeDAO.employeeAdd(employeeName, age, pic))
   response.sendRedirect("success.jsp");
  else
   response.sendRedirect("index.jsp");

}

/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

doGet(request,response);
}

/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}

}

此Servlet只是简单的获取页面输入的数据，其中获取的Pic为用户选择的图片路径。严格讲，获取文件需要经过验证，防止非法图片的选择，这个可以根据自己的需要改善。然后Servlet调用业务类，将获取的数据通过参数传入，进行数据的增加。其中employeeAdd方法实现数据的保存，代码如下：

public boolean employeeAdd(String employeeName,int age,String pic){
  Connection conn=null;
  PreparedStatement pstmt=null;
  FileInputStream fis=null;
  try{
   Class.forName("net.sourceforge.jtds.jdbc.Driver");
   conn=DriverManager.getConnection("jdbc:jtds:sqlserver://localhost:1433/SampleDB","sa","");
   fis=new FileInputStream(pic);

   String strSQL="INSERT INTO employeeInfo VALUES(?,?,?)";
   pstmt=conn.prepareStatement(strSQL);
   pstmt.setString(1, employeeName);
   pstmt.setInt(2, age);
   pstmt.setBinaryStream(3, fis, fis.available());
   if(pstmt.executeUpdate()>0)
    return true;
   else
    return false;
  }catch(ClassNotFoundException ex){
   ex.printStackTrace();
   return false;
  }catch(SQLException ex){
   ex.printStackTrace();
   return false;
  }catch(IOException ex){
   ex.printStackTrace();
   return false;
  }finally{
   try{
    fis.close();
    pstmt.close();
    conn.close();
   }catch(Exception ex){

   }
  }
}

注意粗体部分，用获取的pic信息（文件路径）创建文件输入流对象，增加pic字段的内容通过流对象增加。

pstmt.setBinaryStream(3, fis, fis.available());
三个参数分别为：参数索引，流对象，流对象大小

当增加成功时，重定向到success.jsp

运行结果如下：

增加后，显示如下代表成功：

那么如何验证图片数据是否保存到了数据库中呢？我们通过再次检索增加的数据，读出增加的图片数据并在页面中显示出来进行验证。

首先建立一个非常简单的页面search.jsp，此页面通过文本框使用户输入要检索的人员的姓名，检索人员的基本信息（不检索图片数据），将检索的人员数据形成JOPO对象，保存到session中，以便页面使用。

POJO类（EmployeeObj)

package com.frank.obj;

public class EmployeeObj {
private int employeeId;
private String employeeName;
private int age;
public int getEmployeeId() {
  return employeeId;
}
public void setEmployeeId(int employeeId) {
  this.employeeId = employeeId;
}
public String getEmployeeName() {
  return employeeName;
}
public void setEmployeeName(String employeeName) {
  this.employeeName = employeeName;
}
public int getAge() {
  return age;
}
public void setAge(int age) {
  this.age = age;
}

}

search.jsp页面代码如下：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <base href="<%=basePath%>">

    <title>My JSP 'search.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

</head>

<body>
    <form action="searchServlet" method="POST">
    employeeName:<input type="text" name="employeeName"/>
    <input type="submit" value="search"/>
    </form>
</body>
</html>

通过searchServlet实现基本信息的检索

package com.frank.action;

import java.io.IOException;
import java.io.PrintWriter;

import com.frank.obj.EmployeeObj;
import com.frank.rule.EmployeeDAO;

public class SearchServlet extends HttpServlet {

/**
* Constructor of the object.
*/
public SearchServlet() {
super();
}

/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}

  String employeeName=request.getParameter("employeeName");
  EmployeeDAO employeeDAO=new EmployeeDAO();
  EmployeeObj employeeObj=employeeDAO.getEmployeeByName(employeeName);
  HttpSession session=request.getSession();
  session.setAttribute("employee", employeeObj);
  response.sendRedirect("display.jsp");
}

doGet(request,response);
}

/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}

}

此Servlet调用业务类的getEmployeeByName方法检索人员基本信息，返回EmployeeObj对象，并放入session中，当然也可以放入request中，根据自己的需要改进。页面检索成功后重定向到display.jsp进行信息的显示（稍后讲解）

getEmployeeByName方法代码如下：

public EmployeeObj getEmployeeByName(String employeeName){
  Connection conn=null;
  PreparedStatement pstmt=null;
  ResultSet rst=null;
  EmployeeObj employeeObj=new EmployeeObj();
  try{
   Class.forName("net.sourceforge.jtds.jdbc.Driver");
   conn=DriverManager.getConnection("jdbc:jtds:sqlserver://localhost:1433/SampleDB","sa","");

   String strSQL="SELECT employeeId,employeeName,age FROM EmployeeInfo WHERE employeeName=?";
   pstmt=conn.prepareStatement(strSQL);
   pstmt.setString(1, employeeName);
   rst=pstmt.executeQuery();
   if(rst.next()){
    employeeObj.setEmployeeId(rst.getInt("employeeId"));
    employeeObj.setEmployeeName(rst.getString("employeeName"));
    employeeObj.setAge(rst.getInt("age"));
    return employeeObj;
   }
   return null;
  }catch(ClassNotFoundException ex){
   ex.printStackTrace();
   return null;
  }catch(SQLException ex){
   ex.printStackTrace();
   return null;
  }finally{
   try{
    pstmt.close();
    conn.close();
   }catch(Exception ex){

   }
  }
}

display.jsp负责显示查询出的结果信息，代码如下：

<%@ page language="java" import="java.util.*,com.frank.obj.*" pageEncoding="ISO-8859-1"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <base href="<%=basePath%>">

    <title>My JSP 'display.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

<%
  EmployeeObj employeeObj=(EmployeeObj)session.getAttribute("employee");
%>
</head>

<body>
    <table width="80" border="15">
    <tr>
      <td width="30%" align="right">EmployeeId</td>
      <td width="70%" align="left"><%=employeeObj.getEmployeeId() %></td>
    </tr>
    <tr>
      <td width="30%" align="right">EmployeeName</td>
      <td width="70%" align="left"><%=employeeObj.getEmployeeName() %></td>
    </tr>
    <tr>
      <td width="30%" align="right">Age</td>
      <td width="70%" align="left"><%=employeeObj.getAge() %></td>
    </tr>
    <tr>
      <td width="30%" align="right">Pic</td>
      <td width="70%" align="left"><img src="displayServlet?employeeId=<%=employeeObj.getEmployeeId() %>"/></td>
    </tr>
    </table>
</body>
</html>

代码非常的简单，只是简单的从session中获取保存的EmployeeObj对象，然后利用jsp表达式将数据成员信息显示到页面上。但是注意粗体部分，因为我们需要将保存的图片数据读出，然后显示成图片。所以在此我们利用Img元素显示图片，而Src利用displayServlet的运行结果输出到客户端，作为图片的显示源。displayServlet包含参数employeeId，用来决定具体显示哪一员工的图片。

displayServlet通过Servlet输出流，将读取的图片数据发送到客户端，代码如下：

package com.frank.action;

import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.frank.rule.EmployeeDAO;

public class DisplayServlet extends HttpServlet {

/**
* Constructor of the object.
*/
public DisplayServlet() {
super();
}

/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}

/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

  response.setContentType("image/gif");
  int employeeId=Integer.parseInt(request.getParameter("employeeId"));
  EmployeeDAO employeeDAO=new EmployeeDAO();
  InputStream is=employeeDAO.getPicById(employeeId);
  int size=is.available();
  byte[] image=new byte[size];
  is.read(image);
  ServletOutputStream out=response.getOutputStream();
  out.write(image);

}

/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}

}
在此，调用业务类的getPicById方法得到图片数据的输入流。然后获取的输入流写到ServletOutputStream，这样可以在Servlet的输出端使用，即img的src中使用

getPicById代码如下：

public InputStream getPicById(int employeeId){
  Connection conn=null;
  PreparedStatement pstmt=null;
  ResultSet rst=null;
  InputStream is=null;
  try{
   Class.forName("net.sourceforge.jtds.jdbc.Driver");
   conn=DriverManager.getConnection("jdbc:jtds:sqlserver://localhost:1433/SampleDB","sa","");

   String strSQL="SELECT pic FROM EmployeeInfo WHERE employeeId=?";
   pstmt=conn.prepareStatement(strSQL);
   pstmt.setInt(1, employeeId);
   rst=pstmt.executeQuery();
   if(rst.next()){
    is=rst.getBinaryStream("pic");
    return is;
   }
   return null;
  }catch(ClassNotFoundException ex){
   ex.printStackTrace();
   return null;
  }catch(SQLException ex){
   ex.printStackTrace();
   return null;
  }finally{
   try{
    pstmt.close();
    conn.close();
   }catch(Exception ex){

   }
  }
}

注意粗体部分

好了，我们可以通过运行结果来进行验证，假设我们搜索名称为Mike的人员数据，那么这样：

点search按钮，运行结果如下：

好了，显示出了检索结果，不但包括人员的基本数据，保存到数据库中的图片数据也被读出并显示成图片。

代码只是利用jsp简单的进行体现，大家可以根据自己的需要进行改进。

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