Getting error while autowiring dataSource - spring-mvc

Question

Am getting an error saying :
exception
javax.servlet.ServletException: Servlet.init() for servlet spring threw exception
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
java.lang.Thread.run(Unknown Source)
root cause
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'loginController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.labs.dao.LoginDao com.labs.controllers.LoginController.loginDao; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'loginDao' defined in file [C:\Program Files\Apache Software Foundation\Tomcat 7.0\wtpwebapps\Annotated\WEB-INF\classes\com\labs\dao\LoginDao.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [com.labs.dao.LoginDao]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Property 'dataSource' is required
org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:289)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1146)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:296)
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:293)
org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:628)
org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)
org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:651)
org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:599)
org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:665)
org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:518)
org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:459)
org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
javax.servlet.GenericServlet.init(GenericServlet.java:160)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
java.lang.Thread.run(Unknown Source)
And here is my controller
#Controller
public class LoginController {
#Autowired
private LoginDao loginDao;
#RequestMapping(value="/login", method=RequestMethod.POST)
public ModelAndView login(#ModelAttribute User user){
if(loginDao.login(user))
return new ModelAndView("success", "user", user);
return new ModelAndView("failure");
}
public void setLoginDao(LoginDao loginDao) {
this.loginDao = loginDao;
}
public LoginDao getLoginDao() {
return loginDao;
}
}
And MyDao
#Repository
public class LoginDao {
#Autowired
private DataSource dataSource;
private JdbcTemplate jdbcTemplate = new JdbcTemplate(getDataSource());
public boolean login(User user){
String name = jdbcTemplate.queryForObject("select name from users where name=? and password=?",new Object[]{user.getUserName(),user.getPassword()},String.class);
if(!name.isEmpty())
return true;
return false;
}
public void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
}
public DataSource getDataSource() {
return dataSource;
}
}
spring configuration is
<context:annotation-config/>
<context:component-scan base-package="com.labs"/>
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource" autowire="byName">
<property name="driverClassName" value="org.postgresql.Driver"/>
<property name="url" value="jdbc:postgresql://localhost:5432/postgres" />
<property name="username" value="postgres"/>
<property name="password" value="Raju"/>
</bean>
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<!-- <property name="viewClass" value=""></property> -->
<property name="prefix" value="/WEB-INF/jsp/"/>
<property name="suffix" value=".jsp"></property>
</bean>

Answer 1

This line is the problem
private JdbcTemplate jdbcTemplate = new JdbcTemplate(getDataSource());
Instance variables are initialized before the constructor is called and before Spring has time to autowire any fields. In other words, dataSource is null and getDataSource() therefore returns null. JdbcTemplate throws an Exception if the DataSource argument is null.
Instead change your code to
private DataSource dataSource;
private JdbcTemplate jdbcTemplate;
#Autowired
public LoginDao(DataSource dataSource) {
this.dataSource = dataSource;
this.jdbcTemplate = new JdbcTemplate(this.dataSource);
}