cdi - Java EE Dependency Injection in Websphere Liberty profile -
i trying use cdi in simple web app runs in websphere liberty profile installed via docker.
however injection fails unless specify scope annotation (e.g. @applicationscoped) on injected bean, though according lot of online tutorials (e.g. this), java ee specs not require this.
below code fails:
helloworldservlet.java
package my.simple.app; import javax.inject.inject; import javax.servlet.servletexception; import javax.servlet.annotation.webservlet; import javax.servlet.http.httpservlet; import javax.servlet.http.httpservletrequest; import javax.servlet.http.httpservletresponse; import java.io.ioexception; import java.io.printwriter; @webservlet("/helloworld") public class helloworldservlet extends httpservlet { static string page_header = "<html><head /><body>"; static string page_footer = "</body></html>"; @inject helloservice helloservice; protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception { printwriter writer = resp.getwriter(); writer.println(page_header); writer.println("<h1>" + helloservice.createhellomessage("world") + "</h1>"); writer.println(page_footer); writer.close(); } } helloservice.java
package my.simple.app; public class helloservice { string createhellomessage(string name) { return "hello " + name + "!"; } } server.xml (docker image websphere-liberty:javaee7)
<server description="default servlet engine"> <httpendpoint id="defaulthttpendpoint" host="*" httpport="9080" httpsport="9443" /> <!-- enable features --> <featuremanager> <feature>servlet-3.1</feature> <feature>cdi-1.2</feature> </featuremanager> </server> however error
error 404: javax.servlet.unavailableexception: srve0319e: [my.simple.app.helloworldservlet] servlet, my.simple.app.helloworldservlet servlet class found, resource injection failure has occurred. @inject java.lang.reflect.field.helloservice reference of type my.simple.app.helloservice null component in app.war module of app application cannot resolved. however once add @applicationscoped helloservice starts working.
what doing wrong?
solution:
in cdi1.2 (which using) default annotated beans discovered. make beans discovered, , explicit discovery mode needs enabled in beans.xml
links:
you can force cdi treat servlet bean , perform injection changing bean discovery mode all.
this article provides useful background , example of this:
<?xml version="1.0" encoding="utf-8"?> <beans xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/xmlschema-instance" xsi:schemalocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/beans_1_1.xsd" bean-discovery-mode="all"> </beans> or, in wdt, can generate right-clicking project , selecting java ee tools -> generate cdi beans deployment descriptor stub, , sure select all drop-down "bean discovery mode" selection.
the downside performance hit since app take longer start up, that's tradeoff make avoid recompiling.
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