如何顯示從數據庫到JSP頁面的圖像

Question

//download_image.jsp file
<%@page import="java.io.InputStream"%>
<%@page import="java.io.OutputStream"%>
<%@page import="java.sql.Blob"%>
<%@page import="java.sql.ResultSet"%>
<%
             //   String username = session.getAttribute("userid").toString();

           try {

                OutputStream oImage;
                DB.Connect.openConnection();
                String query = "select image from tbluser where userid = '1'";
                ResultSet rs = DB.Connect.stat.executeQuery(query);
                if (rs.next()) {
                    byte barray[] = rs.getBytes(1);
                    response.reset();                   
                    response.setContentType("image/jpeg");
                    oImage = response.getOutputStream();
                    oImage.write(barray);
                    oImage.flush();
                    oImage.close();
                }
               DB.Connect.CloseConnection();
            } catch (Exception e) {
                e.printStackTrace();
            }
%

塊引用

這是我的代碼，用於顯示mysql db中的圖像。 當我從此標簽的另一個jsp文件調用此文件時，出現錯誤

<img border="3" src="download_image.jsp" height="145" width="145" />

如下：

WARNING: StandardWrapperValve[jsp]: PWC1406: Servlet.service() for servlet jsp threw exception
java.lang.IllegalStateException: PWC3991: getOutputStream() has already been called for this response
        at org.apache.catalina.connector.Response.getWriter(Response.java:707)
        at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:224)
        at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:187)
        at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:180)
        at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:237)
        at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:181)
        at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:132)
        at org.apache.jsp.download_005fimage_jsp._jspService(download_005fimage_jsp.java from :99)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:109)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:406)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:483)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:373)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
        at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:641)
        at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:97)
        at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:85)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:185)
        at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:325)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:226)
        at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:165)
        at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791)
        at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693)
        at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954)
        at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170)
        at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135)
        at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102)
        at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88)
        at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76)
        at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53)
        at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57)
        at com.sun.grizzly.ContextTask.run(ContextTask.java:69)
        at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330)
        at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309)
        at java.lang.Thread.run(Thread.java:619)

我該怎么辦，請給我建議一種方法。

---

我已經在displayImage servlet中編寫了以下代碼，並且在web.xml中也進行了映射，但是圖像上仍然空白:(

public class displayImage extends  HttpServlet{
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
        //PrintWriter pw = response.getWriter();
        String connectionURL = "jdbc:mysql://localhost/medico";
        java.sql.Connection con=null;
        try{
        Class.forName("com.mysql.jdbc.Driver").newInstance();
            con=DriverManager.getConnection(connectionURL,"root","");
            Statement st1=con.createStatement();
            ResultSet rs1 = st1.executeQuery("select image from tbluser where userid='1'");
            String imgLen="";
            if(rs1.next()){
                imgLen = rs1.getString(1);

            }
            rs1 = st1.executeQuery("select image from tbluser where userid='1'");
            if(rs1.next()){
                int len = imgLen.length();
                byte [] rb = new byte[len];
                InputStream readImg = rs1.getBinaryStream(1);
                int index=readImg.read(rb, 0, len);             
                st1.close();
                response.reset();
                response.setContentType("image/jpg");               response.getOutputStream().write(rb,0,len);
                response.getOutputStream().flush();
            }
        }
        catch (Exception e){
            e.printStackTrace();
        }
    }

}

我在html文件中將其稱為。 所以錯誤在哪里:(這里

Answer 1

我不會顯示來自JSP的圖像。 JSP旨在為HTML頁面提供服務，因此它將執行的操作是開始輸出HTTP標頭，說它是輸出流的HTML頁面。

然后在中間，您說的是“哦，不，我想發送圖像”，但是到那時它已經太遲了，這就是為什么您收到此錯誤getOutputStream() has already been called for this response 。

使用JSP輸出圖像沒有任何好處，JSP的要點是使輸出HTML頁面變得容易。

請改用普通的servlet。 覆蓋doGet()方法，然后將輸出圖像的代碼放入其中。 不要忘記將servlet映射添加到web.xml，以便為它提供路徑。

因此，如果您的servlet映射將映射到路徑/downloadImg ，則只需將<img border="3" src="downloadImg" height="145" width="145" />放在另一個JSP中即可。

Answer 2

他們的錯誤在這里：

String connectionURL = "jdbc:mysql://localhost/medico";

您必須提到端口號：您應該將代碼更改為

String connectionURL = "jdbc:mysql://localhost:3306/medico";