Spring injected bean is null - spring

Question

I am using Spring Framework / Data / HATEOAS and trying to add Dozer.
I have the following bean in my spring-config.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:data="http://www.springframework.org/schema/data/jpa"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/data/jpa
http://www.springframework.org/schema/data/jpa/spring-jpa.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd">
<bean id="jpaVendorAdapter" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="database" value="POSTGRESQL" />
<property name="databasePlatform" value="org.hibernate.dialect.PostgreSQLDialect" />
</bean>
<bean id="jpaDialect" class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" />
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory" />
<property name="dataSource" ref="dataSource" />
<property name="jpaDialect" ref="jpaDialect" />
</bean>
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="org.postgresql.Driver" />
<property name="url" value="jdbc:postgresql://localhost:5432/cp" />
<property name="username" value="cp_user" />
<property name="password" value="+JMJ+pw0m2d" />
</bean>
<context:component-scan base-package="com.mydomain.data.assembler" />
<data:repositories base-package="com.mydomain.repository" />
<mvc:annotation-driven />
<bean id="dozerFactory" class="org.dozer.spring.DozerBeanMapperFactoryBean" scope="singleton">
<property name="mappingFiles" value="classpath*:/*mapping.xml"/>
</bean>
</beans>
And the following assembler:
#Component
public class UserResourceAssembler {
#Inject
private Mapper dozerBeanMapper;
public UserResource toResource(User user) {
UserResource resource = dozerBeanMapper.map(user, UserResource.class);
resource.add(linkTo(methodOn(UserController.class).get(user.getId())).withSelfRel());
return resource;
}
public User toEntity(UserResource resource) {
User user = dozerBeanMapper.map(resource, User.class);
return user;
}
}
So, - I'm very new to beans and injection - but I guess that the factory bean is ?supposed? to inject the Mapper. But the Mapper is definitely null. I know I'm not doing this right, but what am I doing wrong?

Answer 1

Spring injects its beans into spring managed beans. You are using an unmanaged static context. Change UserResourceAssembler into a managed bean as well:
#Component
public class UserResourceAssembler {
#Inject
private Mapper dozerBeanMapper;
public UserResource toResource(User user) {
}
public User toEntity(UserResource resource) {
}
}
See why can't we autowire static fields in spring.

Answer 2

I would have preferred something like the above. But then I read:
Dozer Singleton Startup Bean injetced as Null
That worked. Here was my implementation.
I removed the bean from spring-config, and the context scan.
I added this class:
#Singleton
public class DozerInstantiator {
public static DozerBeanMapper getInstance(){
return MapperHolder.instance;
}
private static class MapperHolder{
static final DozerBeanMapper instance = new DozerBeanMapper();
}
}
And updated my assembler like this:
public class UserResourceAssembler {
private DozerBeanMapper mapper;
public UserResourceAssembler() {
mapper = DozerInstantiator.getInstance();
}
public UserResource toResource(User user) {
UserResource resource = mapper.map(user, UserResource.class);
resource.add(linkTo(methodOn(UserController.class).get(user.getId())).withSelfRel());
return resource;
}
public User toEntity(UserResource resource) {
User user = mapper.map(resource, User.class);
return user;
}
}