如何在JSP中使用标记显示图像 [英] How to display an image using tag in JSP

问题描述

以下是在动作类中检索图像的代码。我试过了，但无法显示它我不知道图像处理。我应该如何在JSP中使用标签来显示图像？

Here is the code to retrieve image in action class. I have tried it, but not able to display it I don't know about the image processing. How should I use tags in JSP to display the image?

public String displayImage()
  {
    Connection con = null;
    PreparedStatement preparedStatement = null;
    ResultSet resultSet = null;
    String sql,result="";
    con=JdbcHelper.getConnection();
    if(con!=null)
    {
      try
      {
        sql = "SELECT INPUT_FILE_BLOB FROM message_details where message_id=?";
        preparedStatement = con.prepareStatement(sql);
        preparedStatement.setString(1, messageid);
        resultSet = preparedStatement.executeQuery();
        if(resultSet.next())
        {
          Blob image = resultSet.getBlob("INPUT_FILE_BLOB");
          System.out.println("=============Image2\n" +image);
          int len1 = (int) image.length();
          System.out.println("=============len1\n" +len1);
          byte [] rb1 = new byte[len1];
          InputStream readImg1 = resultSet.getBinaryStream(1);
          try {
            int index1=readImg1.read(rb1, 0, len1);
            System.out.println("index1"+index1);
            response.reset();
            response.setContentType("image/jpg");
            response.getOutputStream().write(rb1,0,len1);
            response.getOutputStream().flush();
          } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
          }
        }
      }
      catch(SQLException e)
      {
        try
        {
          con.rollback();
        }
        catch (SQLException e1)
        {
          result = e1.getMessage();
          e.printStackTrace();
        }
        result = e.getMessage();
        e.printStackTrace();
      }
      finally
      {
        JdbcHelper.close(resultSet);
        JdbcHelper.close(preparedStatement);
        JdbcHelper.close(con);
      }
    }
    else
      result = Constants.SUCCESS;

  }

推荐答案

检索后数据库中的图像为 Blob 或您直接写入响应的字节数组。在这种情况下，您不应该返回SUCCESS结果，您需要返回NONE结果。然后在JSP中，您可以使用 img 标记将图像作为单独的线程访问，该标记将调用返回图像的操作。

After retrieving an image from the database as Blob or byte array you are writing direct to response. In this case you should not return SUCCESS result, you need to return NONE result. Then in the JSP you could access an image as a separate thread using img tag that will call your action that return an image.

另见我们如何显示可以作为字节数组提供的动态或静态图像，
和如何在Struts2中显示图像。

这篇关于如何在JSP中使用标记显示图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！