Question

如何从数据库中检索图像（带有blob数据的mysql）并在servlet中以表格形式<h2>Just some shapes : </h2> <div class="square"></div> <div class="triangle"></div>设置它并在JSP页面上显示它，动态创建表格（基于我的数据库数据）（虽然我不确定它是否可以实现）但如果它是可以实现的，我该怎么做呢？如果无法实现。建议的答案是什么？非常感谢您的帮助。这是我的代码：

(PrintWriter pw = response.getWriter(); pw.write("<img src=""/>"); )

这是我的豆子

     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
             byte[] binaryStream;
        ArrayList<RetrievingPost> combine=new ArrayList<RetrievingPost>();

           try{
                             // Register JDBC driver
                             Class.forName("com.mysql.jdbc.Driver");

                             // Open a connection
                             Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/asq?characterEncoding=UTF-8&useSSL=false", "root", "root");

                             // Execute SQL query
                             Statement pst = connection.createStatement();
                             String sql;
                             sql = "select profilepic, displayname, r.userId, friendId from registration r inner join friendlist fl on r.userId=fl.userId where r.emailAddress='" + emailAddress + "'";
                             ResultSet rs = pst.executeQuery(sql);

                             // Extract data from result set
                             while(rs.next()){
                                //Retrieve by column name
                         Retrieving retrieve=new Retrieve();
                                userId  = rs.getInt("userId");
                                 System.out.println(userId+"---------userId-------");
                                friendId =rs.getInt("friendId");
                                displayname=rs.getString("displayname");

                              binaryStream = rs.getBytes("profilepic");
    retrieve.setFriendId(friendId);
    retrieve.setDisplayName(displayname);
     retrieve.setBinaryStream(binaryStream);
     Combine.add(retrieve);
                        }


                             // Clean-up environment
                             rs.close();
                             pst.close();
                             connection.close();
                          }catch(SQLException se){
                             //Handle errors for JDBC
                             se.printStackTrace();
                          }catch(Exception e){
                             //Handle errors for Class.forName
                             e.printStackTrace();
                          }finally{
                             //finally block used to close resources
                             try{
                                if(stmt!=null)
                                   stmt.close();
                             }catch(SQLException se2){
                             }// nothing we can do
                             try{
                                if(conn!=null)
                                conn.close();
                             }catch(SQLException se){
                                se.printStackTrace();
                             }//end finally try
                          } //end try

        for(int j=0;j<combine.size();j++){
          PrintWriter pw = response.getWriter();
                                       pw.write("<HTML><BODY>");
                                       pw.write("<TABLE border='1'>");
                                       pw.write("<TR>");
                                       pw.write("<TD>");



                                       pw.write(combine.get(i).getDisplayname());
                                       pw.write("</TD>");
                                    //if possible, i would like to display my image into the table
                                       pw.write("<TD>");
                                       String tPosted=combine.get(i).getTimePosted().toString();
                                       pw.write(tPosted);
                                       pw.write("</TD>");
                                       pw.write("</TR>");
                                     }}
getServletContext().getRequestDispatcher("/DisplayingImage.jsp").include(request, response);}

Answer 1

查看此question的答案。专注于servlet说明，因为您将它用于您的页面。

基本上，要遵循的流程是：

创建一个servlet，其唯一目的只是调度图像，并确保通过GET参数接收用户的id（例如，创建一个名为 ImageServlet 的servlet，参数 userId 。

@WebServlet("/ImageServlet")
public class ImageServlet extends HttpServlet {
//...
   public void doGet( HttpServletRequest request, HttpServletResponse response){
      Integer userId = Integer.parseInt( request.getParameter( "userId" ) );

在该servlet中，连接到您的数据库。

public void doGet( /*...*/ ){
   Integer userId = //...
   //super method to extract the data from your DB
   RetrievingPost userInfo = new UserDAO( ).fetchById( userId );

超级重要将回复的mime类型标记为“image / jpg”（或png，jpeg等）。
```
response.setContentType( "image/jpg" );
```

提取图像并将其写入outputStream对象。使用一些I / O缓冲区来帮助您

BufferedOutputStream bos = new BufferedOutputStream( response.getOutputStream( ) );
bos.write( userInfo.getBinaryStream( ) );
bos.flush( );
bos.close( );

修改

在JSP页面（或HTML）中放置一个引用servlet的图像标记。

 <img src="/my_project/ImageServlet?userId=50"/>

使用servlet从mysql中检索图像（blob）并在jsp中显示它

1 个答案: