java - How to retrieve and display images from a database in a JSP page? -

how can retrieve , display images database in jsp page?

let's see in steps should happen:

• jsp view technology supposed generate html output.
• to display image in html, need html <img> element.
• to let locate image, need specify src attribute.
• the src attribute needs point valid http:// url , not local disk file system path file:// never work when server , client run @ physically different machines.
• the image url needs have image identifier in either request path (e.g. http://example.com/context/images/foo.png) or request parameter (e.g. http://example.com/context/images?id=1).
• in jsp/servlet world, can let servlet listen on url pattern /images/*, can execute java code on specific url's.
• images binary data , obtained either byte[] or inputstream db, jdbc api offers resultset#getbytes() , resultset#getbinarystream() this, , jpa api offers @lob this.
• in servlet can write byte[] or inputstream outputstream of response usual java io way.
• the client side needs instructed data should handled image, @ least content-type response header needs set well. can obtain right 1 via servletcontext#getmimetype() based on image file extension can extend and/or override via <mime-mapping> in web.xml.

that should it. writes code itself. let's start html (in jsp):

<img src="${pagecontext.request.contextpath}/images/foo.png"> <img src="${pagecontext.request.contextpath}/images/bar.png"> <img src="${pagecontext.request.contextpath}/images/baz.png"> 

you can if necessary dynamically set src el while iterating using jstl:

<c:foreach items="${imagenames}" var="imagename">     <img src="${pagecontext.request.contextpath}/images/${imagename}"> </c:foreach> 

then define/create servlet listens on requests on url pattern of /images/*, below example uses plain vanilla jdbc job:

@webservlet("/images/*") public class imageservlet extends httpservlet {      // content=blob, name=varchar(255) unique.     private static final string sql_find = "select content image name = ?";      @resource(name="jdbc/yourdb") // tomcat, define <resource> in context.xml , declare <resource-ref> in web.xml.     private datasource datasource;      @override     protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {         string imagename = request.getpathinfo().substring(1); // returns "foo.png".          try (connection connection = datasource.getconnection(); preparedstatement statement = connection.preparestatement(sql_find)) {             statement.setstring(1, imagename);              try (resultset resultset = statement.executequery()) {                 if (resultset.next()) {                     byte[] content = resultset.getbytes("content");                     response.setcontenttype(getservletcontext().getmimetype(imagename));                     response.setcontentlength(content.length);                     response.getoutputstream().write(content);                 } else {                     response.senderror(httpservletresponse.sc_not_found); // 404.                 }             }         } catch (sqlexception e) {             throw new servletexception("something failed @ sql/db level.", e);         }     }  } 

that's it. in case worry head , caching headers , responding on requests, use abstract template static resource servlet.

see also:

• how should connect jdbc database / datasource in servlet based application?
• how upload image , save in database?
• simplest way serve static data outside application server in java web application