showbookimgtag.java

一个简单的购物网站,包括购物车的实现

package csai.tag;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.servlet.ServletOutputStream;
import javax.servlet.jsp.tagext.TagSupport;
import javax.sql.DataSource;
/**
 * @author dengziyun
 * 显示书藉图片的Tag处理类
 */
public class showBookImgTag extends TagSupport{
	public long book_id;
	//----标签开始时调用此方法-------
	public int doStartTag(){
		try{
			//------连接数据库并得到图片字段值------
			Context initCtx = new InitialContext(); 
			Context ctx = (Context) initCtx.lookup("java:comp/env");
			//获取连接池对象           
			Object obj = (Object) ctx.lookup("jdbc/sqlserver");    
			//类型转换         
			DataSource ds = (javax.sql.DataSource)obj;
			//得到数据库连接
			Connection conn = ds.getConnection();
			//得到图片字段值
			Statement stmt = conn.createStatement(); 
			String strSql = "SELECT book_id,book_image from book where book_id="+book_id; 
			ResultSet rs = stmt.executeQuery(strSql);
			if(rs!=null){
				rs.next();
	            InputStream in=rs.getBinaryStream("book_image"); 
	            if(in!=null){
	            	byte[] tempByteArray=toImageByteArray(in);
	            	//------得到页面的输出流------
	            	ServletOutputStream tempOutStream=pageContext.getResponse().getOutputStream();
	            	//------输出图片------
	            	tempOutStream.write(tempByteArray);
	            	tempByteArray=null;
	            }
	            in=null;
	            rs.close();
	            conn.close();   
			}
		}catch(Exception e){
			e.printStackTrace();
		}
		return SKIP_BODY;
	}
	//------得到图片的字节数组------
	private byte[] toImageByteArray(InputStream in){
		if(in!=null){
            try{
                int len = 10*1024*1024;
                byte[] P_Buf = new byte[len];
                int j;
                byte[] newByteArray = null;
                if((j = in.read(P_Buf)) != -1) {
                	newByteArray=new byte[j];
                	for(int k=0;k<j;k++)
                    	newByteArray[k]=P_Buf[k];
                }
                P_Buf=null;
                return newByteArray;
            }catch(Exception e1){
                e1.printStackTrace();
            }
        }
		return null;
	}
	
	public long getBook_id() {
		return book_id;
	}
	public void setBook_id(long book_id) {
		this.book_id = book_id;
	}
}