Problems using Hibernate and Spring in web application
I'm having NullPointerException trying to getCurrentSession()
java.lang.NullPointerException
servlets.ControlServlet.doPost(ControlServlet.java:46)
javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
I use Tomcat 5.5 index.jsp page:
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title></title>
</head>
<body>
<%@ page import="java.util.List" %>
<%@ page import="data.Singer" %>
<jsp:useBean id="singer" class="data.Singer" scope="session"/>
<jsp:setProperty name="singer" property="*" />
<form action="ControlServlet" method="POST">
<form method=“POST”>
Name:<br />
<input type=“text” name="name" /><br />
Type:&l开发者_如何转开发t;br />
<input type=“text” name="type" /><br />
<input type="submit" name="Add song" value="Add song">
<input type="submit" name="save" value="Save" /><br><br>
<input type ="submit" name="values" value="Get values" >
</form>
</body>
</html>
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<display-name>webproject</display-name>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/beans.xml, /WEB-INF/conf.xml, /WEB-INF/singers.hbm.xml, /WEB-INF/songs.hbm.xml, /WEB-INF/singerbeans.xml, /WEB-INF/songbeans.xml</param-value>
</context-param>
<servlet>
<servlet-name>context</servlet-name>
<servlet-class>org.springframework.web.context.ContextLoaderServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet>
<servlet-name>test</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>test</servlet-name>
<url-pattern>*.*</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>action</servlet-name>
<servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
<init-param>
<param-name>config</param-name>
<param-value>/WEB-INF/beans.xml, /WEB-INF/conf.xml, /WEB-INF/singers.hbm.xml, /WEB-INF/songs.hbm.xml, /WEB-INF/singerbeans.xml, /WEB-INF/songbeans.xml</param-value>
</init-param>
<init-param>
<param-name>debug</param-name>
<param-value>2</param-value>
</init-param>
<init-param>
<param-name>detail</param-name>
<param-value>2</param-value>
</init-param>
<load-on-startup>2</load-on-startup>
</servlet>
<servlet>
<description>
</description>
<display-name>ControlServlet</display-name>
<servlet-name>ControlServlet</servlet-name>
<servlet-class>servlets.ControlServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>action</servlet-name>
<url-pattern>*.*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>ControlServlet</servlet-name>
<url-pattern>/ControlServlet</url-pattern>
</servlet-mapping>
</web-app>
ControlServlet.java
public class ControlServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
@Autowired
private SingerDao singerdao;
public SingerDao getSingerDao() {
return singerdao;
}
public void setSingerDao(SingerDao singerdao) {
this.singerdao = singerdao;
}
public ControlServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
if (request.getParameter("values") != null) {
response.getWriter().println(singerdao.getDBValues());
}
}
}
and SingerDao.java
public class SingerDao implements SingerDaoInterface {
@Autowired
private SessionFactory sessionFactory;
public void setSessionFactory(SessionFactory sessionFactory) {
this.sessionFactory = sessionFactory;
}
public List getDBValues() {
Session session = getCurrentSession();
List<Singer> singers = session.createCriteria(Singer.class).list();
return singers;
}
private org.hibernate.classic.Session getCurrentSession() {
return sessionFactory.getCurrentSession();
}
public void updateSinger(Singer singer) {
Session session = getCurrentSession();
session.update(singer);
}
public Singer getSinger(int id) {
Singer singer = null;
Session session = getCurrentSession();
singer = (Singer) session.load(Singer.class, id);
return singer;
}
public void deleteSinger(Singer singer) {
Session session = getCurrentSession();
session.delete(singer);
}
public void insertRow(Singer singer) {
Session session = getCurrentSession();
session.save(singer);
}
}
In simple Java Project it works fine.I think sessionFactory doesn't autowires,but why? Thanks all.
You can't use @Autowired in plain servlets since they are not managed by Spring.
However you can use the following trick to initiate autowiring of servlet manualy:
public class ControlServlet extends HttpServlet {
@Autowired
private SingerDao singerdao;
public void init(ServletConfig cfg) {
super.init(cfg);
WebApplicationContextUtils
.getWebApplicationContext(cfg.getServletContext())
.getAutowireCapableBeanFactory()
.autowireBean(this);
}
...
}
Also, as suggested in comments, since you already have Spring MVC's DispatcherServlet in your setup perhaps it would be better to implement functionality of ControlServlet as a Spring MVC controller rather than servlet (unless you have strong reasons to do it as a servlet).
The stack trace tells you that the NPE occurs at line 46 of the ControlServlet class, ine the method doPost. This is certainly the line where you try to invoke a method of the singerdao object.
So this is the property that isn't being injected. And it's not surprising, because the Servlet is instantiated by the web container, and not by Spring. Spring doesn't know anything about this servlet, and can't inject anything into it.
加载中,请稍侯......
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