Error creating bean in spring , Constructor threw exception; nested exception is java.lang.NullPointerException

When i autowire SessionFactory it works fine, but as i open my session using

Session session = sessionFactory.openSession()

it gives the following error

SEVERE: Exception sending context initialized event to listener instance of class [org.springframework.web.context.ContextLoaderListener]
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'adminController': Unsatisfied dependency expressed through field 'categoryService'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'categoryService': Unsatisfied dependency expressed through field 'categoryDao'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'categoryDao' defined in file [D:\eclipse-workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\exuberancesolutions\WEB-INF\classes\com\exuberancesolutions\daoImpl\CategoryDaoImpl.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.exuberancesolutions.daoImpl.CategoryDaoImpl]: Constructor threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:643)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:130)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1422)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:594)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:879)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:401)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:292)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:103)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:5134)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5662)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
    at org.apache.catalina.core.StandardContext.reload(StandardContext.java:4153)
    at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:446)
    at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1461)
    at org.apache.catalina.core.StandardContext.backgroundProcess(StandardContext.java:6004)
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1660)
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1670)
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1670)
    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1638)
    at java.base/java.lang.Thread.run(Thread.java:844)
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'categoryService': Unsatisfied dependency expressed through field 'categoryDao'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'categoryDao' defined in file [D:\eclipse-workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\exuberancesolutions\WEB-INF\classes\com\exuberancesolutions\daoImpl\CategoryDaoImpl.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.exuberancesolutions.daoImpl.CategoryDaoImpl]: Constructor threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:643)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:130)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1422)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:594)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1287)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1207)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640)
    ... 27 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'categoryDao' defined in file [D:\eclipse-workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\exuberancesolutions\WEB-INF\classes\com\exuberancesolutions\daoImpl\CategoryDaoImpl.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.exuberancesolutions.daoImpl.CategoryDaoImpl]: Constructor threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1320)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1214)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1287)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1207)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640)
    ... 40 more
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.exuberancesolutions.daoImpl.CategoryDaoImpl]: Constructor threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:216)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:87)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1312)
    ... 51 more
Caused by: java.lang.NullPointerException
    at com.exuberancesolutions.daoImpl.CategoryDaoImpl.<init>(CategoryDaoImpl.java:19)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:488)
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:203)
    ... 53 more

HibernateConfig.java

package com.exuberancesolutions.config;

import java.util.Properties;

import javax.sql.DataSource;

import org.apache.tomcat.dbcp.dbcp.BasicDataSource;
import org.hibernate.SessionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.orm.hibernate5.HibernateTransactionManager;
import org.springframework.orm.hibernate5.LocalSessionFactoryBuilder;
import org.springframework.transaction.annotation.EnableTransactionManagement;



@Configuration
@ComponentScan("com.exuberancesolutions.entity")
@EnableTransactionManagement
public class HibernateConfig {
    private final static String DATABASE_URL = "jdbc:mysql://127.0.0.1:3306/rajeev?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC";
    private final static String DATABASE_DRIVER = "com.mysql.jdbc.Driver";
    private final static String DATABASE_DAILECT = "org.hibernate.dialect.MySQL57Dialect";
    private final static String DATABASE_USERNAME = "root";
    private final static String DATABASE_PASSWORD = "";

    @Bean
    public DataSource getDataSource() {
        BasicDataSource dataSource = new BasicDataSource();
        dataSource.setDriverClassName(DATABASE_DRIVER);
        dataSource.setUrl(DATABASE_URL);
        dataSource.setUsername(DATABASE_USERNAME);
        dataSource.setPassword(DATABASE_PASSWORD);
        return dataSource;
    }

    @Bean
    @Autowired
    public SessionFactory getSessionFactory(DataSource dataSource) {
        LocalSessionFactoryBuilder builder = new LocalSessionFactoryBuilder(dataSource);
        builder.addProperties(getHibernateProperties());
        builder.scanPackages("com.exuberancesolutions.entity");
        return builder.buildSessionFactory();
    }

    private Properties getHibernateProperties() {
        Properties properties = new Properties();
        properties.put("hibernate.dialect",DATABASE_DAILECT);
        properties.put("hibernate.show.sql","true");
        properties.put("hibernate.hbm2ddl.auto","create");
        return properties;
    }
    @Bean
    @Autowired
    public HibernateTransactionManager getTransactionManager(SessionFactory sessionFactory) {
        HibernateTransactionManager tm = new HibernateTransactionManager(sessionFactory);
        return tm;
    }
}

DaoImpl.java

package com.exuberancesolutions.daoImpl;




import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

import com.exuberancesolutions.dao.CategoryDao;
import com.exuberancesolutions.entity.Category;

@Repository("categoryDao")
public class CategoryDaoImpl implements CategoryDao {
    @Autowired
    SessionFactory sessionFactory;
    Session session = sessionFactory.openSession();
    Transaction tx = null;
    @Override
    public boolean save(Category category) {
        // TODO Auto-generated method stub if inserted return true, other false
        return false;
    }

}

If you need any other code please let me know, i have checked my versions the seems good.

i tryed using xml it worked fine, but can find whats wrong in this code. i'm stuck in middle of no where, a help would be appreciated.

Solution

This is the issue:

@Autowired
SessionFactory sessionFactory;
Session session = sessionFactory.openSession(); //Issue is here

You are trying to get a session, when sessionFactory is not available yet, as the sessionFactory is only Autowired after the categoryDao has been constructed.

Do this:

@Autowired
SessionFactory sessionFactory;
Session session;

@PostConstruct
public void init() {
    session = sessionFactory.openSession();
}

In short, it's all about order of construction.

Note: Constructor injection would have worked too, and you wouldn't need the @PostConstruct.