Spring autowired dao is null

Question

I am attempting to create rest web services to handle CRUD operations for an android application. I'm using Spring 4.0 with Hibernate. I'm trying to autowire a dao and it's always null and I haven't been able to figure out the cause of the issue. I searched online and everything looks right to me so I'm at a complete lost. I defined the bean in the applicationContext as I have saw in many tutorials but I'm unable to get the dao to autowire. Any help would be appreciated.

dispatch-servlet.xml

<?xml version='1.0' encoding='UTF-8' ?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
       http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
       http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
       http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">


    <context:annotation-config />
    <mvc:annotation-driven />
    <context:component-scan base-package="com.bike.party.services, com.bike.party.daos" />
  <tx:annotation-driven transaction-manager="transactionManager"  />

</beans>

applicationContext.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:p="http://www.springframework.org/schema/p" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd">

   <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer" id="propertyConfigurer" p:location="/WEB-INF/jdbc.properties"/>

<bean class="org.springframework.jdbc.datasource.DriverManagerDataSource" id="dataSource" p:driverClassName="${jdbc.driverClassName}" p:password="${jdbc.password}" p:url="${jdbc.url}" p:username="${jdbc.username}"/>

    <!-- ADD PERSISTENCE SUPPORT HERE (jpa, hibernate, etc) -->
    <bean class="org.springframework.orm.hibernate4.LocalSessionFactoryBean" id="sessionFactory">
        <property name="dataSource" ref="dataSource"/>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">${hibernate.dialect}</prop>
                <prop key="hibernate.show_sql">true</prop>

            </props>
        </property>
        <property name="packagesToScan" value="com.bike.party.models"/>
    </bean>

    <bean class="org.springframework.orm.hibernate4.HibernateTransactionManager" id="transactionManager" p:sessionFactory-ref="sessionFactory" />    

    <tx:annotation-driven/>
</beans>

UserDao

package com.bike.party.daos;

import com.bike.party.models.User;

public interface UserDao extends Dao<User> {

    public User findByUserName(String username);
}

UserDaoImpl

package com.bike.party.daos;

import com.bike.party.models.User;
import java.util.List;
import javax.transaction.Transactional;
import org.hibernate.SessionFactory;
import org.hibernate.criterion.Restrictions;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Repository;

@Repository
@Transactional
@Qualifier("userDaoImpl")
public class UserDaoImpl implements UserDao {

    @Autowired
    private SessionFactory sessionFactory;

    @Override
    public User findByUserName(String username) {
        List<User> userList = sessionFactory.getCurrentSession().createCriteria(User.class).add(Restrictions.eq("username", username)).setMaxResults(1).list();
        return userList.isEmpty() ? null : userList.get(0);
    }
}

UserWebService

package com.bike.party.services;

import com.bike.party.daos.UserDao;
import com.bike.party.models.User;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.ext.Provider;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Provider
@Component
@Path("userservice")
public class UserWebService {

    @Autowired
    private UserDao userDao;

    @GET
    @Path("/user/{username}")
    @Produces(MediaType.TEXT_PLAIN)
    public String getUser(String username) {
        if (userDao == null) {
            return "the dao is null";
        }

        User user = userDao.findByUserName(username);
        if (user == null) {
            return "No user was found.";
        } else {
            return user.getUsername();
        }
    }
}

UPDATE:

I modified the UserWebService with

private UserDao userDao;

    @Autowired
    public void setUserDao(UserDao userDao) {
        if (functionDao != null) {
            System.out.println(String.valueOf(userDao.findByUserName("chris")));
        } else {
            System.out.println("setting the dao is null :(");
        }
        this.userDao= userDao;
    }

When the web app is deployed this is called and finds the user but when I call it from the client it is always null. Could this be because I'm calling the service directly and not going through spring? If so could any point me to the create way to call the service from the client. Thanks

Answer 1

i believe spring can not find your UserDao class.

try to change your component-scan instruction in dispatch-servlet.xml to this one:

<context:component-scan base-package="com.bike.party.*" />

If you're using Spring Tool Suite all @Component 's in your project should be marked as Component(icon with S ):

EDIT: remove bean definition from xml, do not mix xml and annotated configuration. Remove also "userDaoImpl" from your Annotations. Change @Repository("userDaoImpl") to @Repository()

Answer 2

Remove the <bean id="userDao" class="com.bike.party.daos.UserDaoImpl" /> bean from the applicationContext.xml file.

I think you are injecting this instance instead of the the one that gets created via the @Repository annotation which is why your SessionFactory is null

Answer 3

尝试从 SpringBeanAutowiringSupport 派生您的 UserWebService。