T3 里的图片显示

T3 里的图片显示

例子参考:
T3自带的workbeanch里有
1.ChartService class
2.ChartAsset class
3.IChartProvider的例子代码

思路:
因为在DAO,service里返回的Info对象里已经有图片的属性,
类型是byte[]
所以直接out.write(byte[])获得图片.

题外:
其中,AbstractService相比T4少了Webresponse属性，
不可以直接在IChartProvider里定义 
public void sendDynaAsset(WebResponse response);
然后在实现类里用这句 
OutputStream out = response.getOutputStream(new ContentType("image/jpeg"));
来操作out.write .
T3里都在AbstractService里操作out, service()方法里就有参数ResponseOutputStream output

代码:
1. ChartService

public   class  ChartService  extends  AbstractService {

  public void service(
        IEngineServiceView engine,
        IRequestCycle cycle,
        ResponseOutputStream output)
        throws ServletException, IOException
    {

.

  try
        {
            IChartProvider provider = (IChartProvider) component;

            byte[] bytes = provider.getImageBytes();

            //默认规则,page页面里若数据库里没有bytes,则返回null
            if (bytes==null)
                //显示默认图片
                bytes = drawDefaultImage();         
            
            output.setContentType("image/jpeg");

            // I've seen a few bits of wierdness (including a JVM crash) inside this code.
            // Hopefully, its a multi-threading problem that can be resolved
            // by synchronizing.

            synchronized (this)
            {
                output.write(bytes);
            }
        }

   }

protected byte[] drawDefaultImage() {
        int width = 102, height = 126;
        BufferedImage image = new BufferedImage(width, height,
                BufferedImage.TYPE_INT_RGB);
        Graphics g = image.getGraphics();

        g.setColor(Color.WHITE);
        g.fillRect(0, 0, width, height);

        g.setColor(Color.RED);
        g.setFont(new Font("Default", Font.PLAIN, 22));
        g.drawString("暂无照片", 10, height / 2 - 10);

        byte buffer[] = null;
        try {
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            ImageIO.write(image, "JPEG", out);
            buffer = out.toByteArray();
        } catch (Exception e) {
            log.info("绘制默认图片失败");
        }
        return buffer;
    }
}

2. ChartAsset
与workbeanch里的CharAsset一样,没有任何增删

public   class  ChartAsset  extends  AbstractAsset {
  private IEngineService _chartService;
  private IComponent _chartProvider;
 public ChartAsset(IRequestCycle cycle, IComponent chartProvider)
    {
        super(null, null);
        
        IEngine engine = cycle.getEngine();

        _chartService = engine.getService(ChartService.SERVICE_NAME);
        _chartProvider = chartProvider;
    }

}

3. IChartProvider
Service类回调接口

public   interface  IChartProvider
{
    public byte[] getImageBytes();
}

4.Page类
需要实现IChartProvider回调接口的getImageBytes()方法

public   abstract  SaryPage  extends  BasePage  implements  IChartProvider {
 private IAsset chartImageAsset;

    public IAsset getChartImageAsset() {
        if (chartImageAsset == null)
            chartImageAsset = new ChartAsset(getRequestCycle(), this);

        return chartImageAsset;
    }
 /** *//**
     * This method is invoked by the service (in a seperate request cycle from
     * all the form handling stuff). The {@link #getChartImageAsset()} method
     * provides an {@link IAsset} that is handled by the {@link ChartService},
     * and the asset encodes the identity of this page.
     * 
     */
    public byte[] getImageBytes() {
        if (getSary().getXp()!=null)
            return getSary().getXp();
        else
            //默认规则,page页面里若数据库里没有bytes,则返回null
            return null;
    }

}

5.  Html页面

< img  jwcid ="@Image"  width ="102"  height ="126"   image ="ognl:chartImageAsset" />

6. .application文件 注册ChartService

< application  name ="SaryProject"  engine-class ="cn.vikings.tapestry.common.SaryEngine" >
    
  < service  name ="chart"  class ="cn.vikings.tapestry.common.chart.ChartService" />

</ application >

图片显示搞店. 就这么简单.
不用再很BT得传一句HQL语句和图片ID来，再用JDBC查一次数据库.