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How to autowire generic types

Time：01-04

I'm new to Spring and I'm trying to autowire a generic DAO. Unfortunately, I'm getting an error. I tried to search info based on it, but most solutions state to use @Qualifier annotation which in my opinion is against what I want to achieve.

So below some code (I'll get rid of that class parameter once I deal with current issue):

DAO

public interface GenericDAO<T> {

    T save(T entity, Class<T> tClass);
    List<T> findAll(Class<T> tClass);
    List<T> findAllByKeyword(String keyword, Class<T> tClass);
    T findById(int id, Class<T> tClass);
    void deleteById(int id, Class<T> tClass);

}

public class GenericDAOImpl<T> implements GenericDAO<T> {

    SessionFactory sessionFactory;


    public GenericDAOImpl(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    @Override
    @Transactional
    public T save(T entity, Class<T> tClass) {
        //body
    }

    //other methods
}

@Repository
public class FooDAOImpl extends GenericDAOImpl<Foo> {

    @Autowired
    public FooDAOImpl(SessionFactory sessionFactory) {
        super(sessionFactory);
    }

Service

public interface GenericService<T> {

    T save(T entity, Class<T> tClass);
    List<T> findAll(Class<T> tClass);
    List<T> findAllByKeyword(String keyword, Class<T> tClass);
    T findById(int id, Class<T> tClass);
    void deleteById(int id, Class<T> tClass);

}

public class GenericServiceImpl<T, T_DAO extends GenericDAO<T>> implements GenericService<T> {


    private final T_DAO dao;

    public GenericServiceImpl(T_DAO dao) {
        this.dao = dao;
    }

    @Override
    public T save(T entity, Class<T> tClass) {
        return dao.save(entity, tClass);
    }

    // other methods
}

@Service
public class FooServiceImpl extends GenericServiceImpl<Foo, FooDAOImpl> {

    @Autowired
    public FooServiceImpl(FooDAOImpl fooDAOImpl) {
        super(fooDAOImpl);
    }
}
}

And error thrown below:

javax.servlet.ServletException: Servlet.init() for servlet [dispatcher] threw exception
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
    org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
    org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1707)
    org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.base/java.lang.Thread.run(Thread.java:834)
Root Cause

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'fooServiceImpl' defined in class path resource [*/*/*/service/FooServiceImpl.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'fooDAOImpl' is expected to be of type '*.*.*.repository.FooDAOImpl' but was actually of type 'com.sun.proxy.$Proxy76'
    org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:797)
    org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:227)
    org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1356)
    org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1203)
    org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556)
    org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
    org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
    org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
    org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
    org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:897)
    org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:879)
    org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551)
    org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:702)
    org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:668)
    org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:716)
    org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:591)
    org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:530)
    org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:170)
    javax.servlet.GenericServlet.init(GenericServlet.java:158)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
    org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
    org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1707)
    org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.base/java.lang.Thread.run(Thread.java:834)
Root Cause

org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'fooDAOImpl' is expected to be of type '*.*.*.repository.FooDAOImpl' but was actually of type 'com.sun.proxy.$Proxy76'
    org.springframework.beans.factory.support.DefaultListableBeanFactory.checkBeanNotOfRequiredType(DefaultListableBeanFactory.java:1736)
    org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1713)
    org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1273)
    org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1227)
    org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:884)
    org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:788)
    org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:227)
    org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1356)
    org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1203)
    org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556)
    org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
    org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
    org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
    org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
    org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:897)
    org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:879)
    org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551)
    org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:702)
    org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:668)
    org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:716)
    org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:591)
    org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:530)
    org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:170)
    javax.servlet.GenericServlet.init(GenericServlet.java:158)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:687)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
    org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
    org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893)
    org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1707)
    org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    java.base/java.lang.Thread.run(Thread.java:834)

CodePudding user response：

The error is that spring has failed to create the bean customerServiceImpl because customerServiceImpl expect a dependency of type CustomerDAOImpl and spring has injected a dependency of com.sun.proxy.$Proxy76

Bean named 'customerDAOImpl' is expected to be of type 
'com.smartdigit.zalewski.repository.CustomerDAOImpl' but was actually of type 
'com.sun.proxy.$Proxy76'

You have to change your FooServiceImpl class in order to get a dependency of type FooDAOInterface and not an implementation of it.

Someting like:

public class FooServiceImpl extends GenericServiceImpl<> {
    @Autowired
    public FooServiceImpl(FooDAOInterface fooDAO) {
    super(fooDAOImpl);
   }
}

You have to pass an interface type in the FooServiceImpl constructor in order to spring autowired it when the spring context has been initilized.

CodePudding user response：

Hi Error is coming due to wrong dependency got passed in constructor.

Please use like this.

@Service
public class FooServiceImpl extends GenericServiceImpl<Foo, FooDAO> {

private final FooDAO fooDAO;
    @Autowired
    public FooServiceImpl(FooDAO fooDAO) {
        this.fooDAO = fooDAO
    }
}

If a bean has one constructor, you can omit the @Autowired

@Service
public class FooServiceImpl extends GenericServiceImpl<Foo, FooDAO> {

private final FooDAO fooDAO;
    
    public FooServiceImpl(FooDAO fooDAO) {
        this.fooDAO = fooDAO
    }
}

Note: FooDAO should be your interface

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