通过Hibernate（不是JDBC）从blob中获取图像 [英] Retrieve image from blob via Hibernate (not JDBC)

问题描述

感谢 ，我发现了很好的从 db / blob <如何从JSP页面中的数据库中检索和显示图像？

I've found very nice solution of retrieving images from db/blob thanks to How to retrieve and display images from a database in a JSP page?

但是这是在每个图像请求上使用 JDBC连接的解决方案。

But this is solution that uses JDBC connection on every image request.

我正在使用 Spring 3 注释和 Hibernate 3 。

我试图用我的'imageService'来做类似的事情，'imageService'是通过 ImageServlet类中的注释自动装配的，但是我得到了空指针异常，这意味着可能 imageService 不是由依赖注入设置的。

I tried to do similar thing by my 'imageService', which is autowired by annotation in ImageServlet class, but I got nullPointerException, which means that may imageService is not set by Dependency Injection.

有没有办法解决这个问题？我不喜欢在图像请求中创建单个jdbc连接。

Is there any way how to solve that? I don't like to make single jdbc connection on image request.

推荐答案

我希望你将图像存储在表中一个BLOB类型（如果不尝试这样做，因为这是最佳实践）。假设你有一个存储在DB中的人的 Person 类和一个图像。如果你想映射这个，只需在你的人POJO中添加一个属性来保存图像。

I hope you are storing the image in the table as a BLOB type(If not try to do so, as this is the best practice). Lets assume you have a Person class with the an image of the person stored in the DB. If you want to map this, just add a property in your person POJO that holds the image.

@Column(name="image")
@Blob
private Blob image;

当您显示它时，将它转换为 byte []


When you display it, convert it to a byte[] and show.

private byte[] toByteArray(Blob fromImageBlob) {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    try {
      return toByteArrayImpl(fromImageBlob, baos);
    } catch (Exception e) {
    }
    return null;
  }



private byte[] toByteArrayImpl(Blob fromImageBlob, 
      ByteArrayOutputStream baos) throws SQLException, IOException {
    byte buf[] = new byte[4000];
    int dataSize;
    InputStream is = fromImageBlob.getBinaryStream(); 

    try {
      while((dataSize = is.read(buf)) != -1) {
        baos.write(buf, 0, dataSize);
      }    
    } finally {
      if(is != null) {
        is.close();
      }
    }
    return baos.toByteArray();
  }

你可以看下面的例子来了解更多。

You can see the below examples to know more about it.

1. http://i-proving.com/2006/08/23/blobs-and-hibernate


2. http://snehaprashant.blogspot.com/2008/08/how-to-store-and- retrieve-blob-object.html


3. http://viralpatel.net/blogs/2011/01/tutorial-save-get-blob-object-spring-3-mvc-hibernate.html

1. http://i-proving.com/2006/08/23/blobs-and-hibernate
2. http://snehaprashant.blogspot.com/2008/08/how-to-store-and-retrieve-blob-object.html
3. http://viralpatel.net/blogs/2011/01/tutorial-save-get-blob-object-spring-3-mvc-hibernate.html

正如您所见，有多种方式可以做到这一点。选择适合你的那个。

As you can see there are multiple ways to do this. Choose the one appropriate for you.

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