I'm trying a new development method.
In mybatis3, I write mapper.java and mapper.xml usually.
I know, the sql statements is corresponded by sqlId(namespace+id).
I want to execute the sql statement like this :
SqlSession sqlSession = sessionFactory.openSession();
return sqlSession.selectList(sqlId, param);
but I get a error:
Cause: java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for mapper.JinBoot.test
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:150)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
at cn.tianyustudio.jinboot.dao.BaseDao.select(BaseDao.java:20)
at cn.tianyustudio.jinboot.service.BaseService.select(BaseService.java:10)
at cn.tianyustudio.jinboot.controller.BaseController.test(BaseController.java:21)
here is my BaseDao.java
public class BaseDao {
private static SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
public static List<Map> select(String sqlId, Map param) {
try {
factoryBean.setDataSource(new DruidDataSource());
SqlSessionFactory sessionFactory = factoryBean.getObject();
SqlSession sqlSession = sessionFactory.openSession();
return sqlSession.selectList(sqlId, param);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
here is UserMapper.xml
<mapper namespace="mapper.JinBoot">
<select id="test" parameterType="hashMap" resultType="hashMap">
select * from user
</select>
</mapper>
the application.properties
mybatis.mapperLocations=classpath:mapper/*.xml
I start the project, the send a http request, after controller and service ,the param 'sqlId' in BaseDao is 'mapper.JinBoot.test' (see error info).
In method 'BaseDao.select', both the parameter and the result type is Map.
So I don't want to create UserMapper.java, I want try it.
How can I resolve it? What's the malpractice of this way？
This does not work because spring boot creates its own SqlSessionFactory. And the option in application.properties that specifies where mappers should be looked for is only set for that SqlSessionFactory. You are creating unrelated session factory in your DAO and it does not know where to load mappers definition.
If you want to make it work you need that you DAO is spring managed so that you can inject mybatis session factory into it and use it in select. This would also require that you convert select into non static method.
As I understand you want to have only one method in you base DAO class and use it in individual specific DAO classes. I would say it makes little sense. If the method returns Map there will be some place that actually maps this generic type to some application specific types. This would probably be in the child DAOs. So you still need to create the API of the child DAO with the signature that uses some input parameters and returns some domain objects. And that's exactly what you want to avoid by not creating mybatis mapper classes.
The thing is that you can treat your mytabis mappers as DAOs. That is you mappers would be your DAOs. And you don't need another layer. As I understand now you have two separate layers - DAO and mappers and you want to remove boilerplate code. I think it is better to remove DAO classes. They are real boilerplate and mybatis mapper can serve as DAO perfectly. You inject it directly to you service and service depends only on the mapper class. The logic of the mapping is in the mapper xml file. See also answer to this question Can Spring DAO be merged into Service layer?
Related
I'm wondering if there is a sort of best practice for the following case.
For instance, I have several services and inject them all as an array into a "factory" service. Then I call a method of this factory and want to get only one service depends on some conditions. After that I execute this service and get a result...
However, some of these services require a random string that I get from a client's request.
Of cause, I can call a service's method with this string as a parameter but several services do not require this string and I'll get "unused variable" in the method.
I guess that I could get service from the factory and then call a setter to add this string into the service. But it does not look like a stateless service.
Is there a more elegant solution to pass parameters that I could not inject into service nor use the setter for it?
Here how it looks in my code
First, I have an interface of all servers that I want to check. The service should support a customer an then it should render information from a DTO.
interface Renderable {
public function supports(Customer $customer);
public function render(CustomerDTO $dto);
}
Next, I have several services. This one uses DTO to render data.
class ServiceOne implements Renderable
{
public function suppots(Customer $customer)
{
return $customer->getPriority() === 1;
}
public function render(CustomerDTO $dto)
{
return 'One: '.$dto->getName();
}
}
However, some services do not need any DTO to render, they just provide a hardcoded value.
class ServiceTwo implements Renderable
{
public function suppots(Customer $customer)
{
return $customer->getPriority() !== 1;
}
// service does not use DTO, it simply output result
// so, I'll get a notice about unused variable
// and I can not remove it from the method since it is in interface
public function render(CustomerDTO $dto)
{
return 'Two';
}
}
This is a factory. It has all services injected as an array. Then it checks and returns the first service that supports a customer instance.
class ServiceFactory
{
/** #var Renderable[] */
private $services;
public function __construct(iterable $services)
{
$this->services = $services;
}
public function getRenderer(Customer $customer)
{
foreach ($this->services as $service)
{
if ($service->supports($customer)
{
return $service;
}
}
}
}
Here like I use factory and its result
$customer = ...; // it comes from a database
$request = ...; // it comes from a http request
$renderService = $factory->getRenderer($customer);
$customerDTO = CustomerDTO::createFromData([
'customerUid' => $customer->getUid(),
'date' => new \DateTime(),
'name' => $request->getSheetUid(),
'tags' => $request->getTags(),
]);
$renderService->render($customerDTO);
So, I have to call Renderer::render with a DTO instance. But some services do not use it to "render" data. I also can not inject it into a renderer service since this object (DTO) is built in a runtime when all services already injected. I also can not inject a RequestStack into service.
Since your parameter came from request - it can't be directly injected into service. Depending on actual logic of your services you can consider one of approaches listed below. Let's call your "random string that came from a client's request" a $requestParam for further reference.
In both cases you will need to get your $requestParam from actual Request object and pass it somewhere else. It can be done in a different ways, I would propose to create listener (e.g. RequestParamListener) for kernel.request event and put here a piece of code that takes parameter from Request and pass it further into this listener. Into approaches listed below I will assume that $requestParam will be passed in this way.
1. Separate provider
You can create separate class (e.g. RequestParamProvider) that will act as provider of this $requestParam for other services. It will receive $requestParam from RequestParamListener and other services that needs to get $requestParam will need to inject this provider and use its getRequestParam() method to obtain required parameter.
From my point of view it is the simplest approach and I would recommend it.
2. Direct injection by factory
Since you have some factory service - you can pass this $requestParam directly into factory and let it to initialize other services. Less flexible because you will need to implement initialization logic by itself and maintain it while project evolves.
3. Direct injection using interface
You can create separate interface (e.g. RequestParamAwareInterface) that will contain setRequestParam() method and let all classes that needs this $requestParam to implement this interface. After that you will need to write separate compiler pass that will collect all such classes (by iterating over ContainerBuilder and looking for implementation of particular interface by class inside service's definition) and pass array of these services to your RequestParamListener. Listener in its turn will be obligated to pass $requestParam for each of given services.
This approach will let your application to grow without need to sync $requestParam injection logic. However it will came at a cost of preliminary instantiation of all affected services regardless of actual further use of created instances.
I got a method able to create a CSV file thanks to StreamedResponse object of Symfony2 framework. I use the method several times so I put a callback parameter to personalise the behavior (I forget the buzz word for this practice in Object-Oriented Programming).
Where is the best place to put this method in a MVC project?
Repository? (Model/DAO/Manager)
Entity? (POPO)
Controller
Service
Through a interface (This object able to create CSV file)
Other
As your logic returns a response, the most adapted context is a controller.
Also, if your logic is called from multiple contexts or by multiple classes of the same context (e.g. controllers), to avoid duplicated code, you have two possibilities (at least) :
1 - Use an AbstractController and make your controllers extends the abstract.
2- Use a service (i.e. CsvManager).
If you want some example implementations, see Symfony2 reusable functions in controllers and the Controller as a service chapter of the Symfony documentation.
An example of service implementation:
// src/AppBundle/Services/CsvManager.php
class CsvManager
{
public function generate(/** params */)
{
// Return your streamed response
}
}
The service declaration :
// app/config/services.yml
services:
# ...
app.csv_manager:
class: AppBundle\Services\CsvManager
Now, you can use the service from all your controllers and other contexts that implements the services container. example:
// src/AppBundle/Controller/TestController.php;
class TestController extends \Symfony\Bundle\FrameworkBundle\Controller\Controller
{
public function printCsvAction()
{
$csvManager = $this->get('app.csv_manager');
return $csvManager->generate(/** params */);
}
}
I have a following problem. I have defined an interface:
#Local
public interface ProductTypeLister {
Collection<ListElement> getList();
}
Also, I have defined an implementation for this thing:
#Stateless(name = "ProductTypeLister")
#Local(ProductTypeLister.class)
public class ProductTypeListerImpl implements ProductTypeLister {
#Override
public Collection<ListElement> getList() {
// Implementation code
}
}
And now I want to use it via annotation:
public class ListProductTypeAction extends ActionHandler {
#EJB
protected ProductTypeLister lister;
#Override
public String execute(HttpServletRequest request) throws ServletException {
request.setAttribute("list", lister.getList());
return "listPage.jsp";
}
}
But I get the NullPointerException, since lister is not filled. Now, the problem is, that ActionHandler is not a derivative of HttpServlet and is not executed by the container itself. Instead, we are using FrontController patter - i.e. there is one servlet that handles all the incoming messages and creates required handlers via a simple construction. And therefore the EJB annotated fields are not filled automatically. However, I can fill this specific case in the following manner:
public ListProductTypeAction() throws NamingException {
InitialContext context = new InitialContext();
lister = (ProductTypeLister) context.lookup("<PATH>/ProductTypeLister");
}
In that case everything works fine, but this means I have to do for every handler the specified lookup with JNDI help, but all I want is to get it with annotation help. Therefore, the main servlet needs the following method:
private void fillHandler(ActionHandler handler) {
// Fill #EJB annotated fields
}
But how can I fill it? Of course, I can manually run through every field and check if it's annotated EJB and fill it using JNDI based on the interface unqualified name. But is there a way to do this using the libraries I already have? After all, Glassfish is supposed to fill those fields during the deployment phase. How can I make him do that for a non-servlet class?
J2EE tutorial
Dependency injection is the simplest way of obtaining an enterprise bean reference. Clients that run within a Java EE server-managed environment,
JavaServer Faces web applications, JAX-RS web services, other
enterprise beans, or Java EE application clients, support dependency
injection using the javax.ejb.EJB annotation.
Applications that run outside a Java EE server-managed environment,
such as Java SE applications, must perform an explicit lookup. JNDI
supports a global syntax for identifying Java EE components to
simplify this explicit lookup.
So even if your class is inside a J2EE container, but its lifecycle is not managed by container, you are out of luck, you have to do it manually.
Below is my controller. My program generates an output, based on a form input. Across the project, there are multiple input forms, that generate the output object. So, the essential flow is the same. So I want a single multi-action controller that does all of that.
Challenges:
1. The service classes change. Although all services implement the same interface, and controller calls the same interface method.
2. The input objects change. Although the input objects do not have any methods other than setters, and getters. So I let them all implement an empty interface.
Questions:
How do I change the qualifier, based on the path. Can I use path variables?
Suppose the path has this value -> singleton. Then my corresponding bean names would be singletonService and singletonInput. I want to make a constant class that has stores this mapping information. So, can I call that from inside the qualifier, using some Spring Expression Language? Example, instead of Qualifier(variablePathName) -> Qualifier(getQualifierName['variablePathName']) Something like that?
Please also clarify the theory behind this. From what I understand, beans are created, autowired before the Request are mapped... Does this mean that what I'm trying to achieve here is simply not possible. In that case, would you suggest making Controller-service pairs for handling each request, with basically the same code? But I feel there must be some way to achieve what I'm trying...
Code:
#Cotroller
#RequestMapping(value="/generate/{path}")
public class TestController {
#Autowired
#Qualifier(......)
private IService service;
#Autowired
#Qualifier(......)
IUserInput userInput;
#RequestMapping(method = RequestMethod.POST)
//Some handler method
}
You're right in that the autowiring is all done once up front (point 3). You wouldn't be able to achieve what you want using fields annotated #Autowired and #Qualifier - as these fields would always reference the same bean instance.
You may be better to ask Spring for the particular service bean by name - based on the path variable. You could do it within a single controller instance. For example:
#Cotroller
#RequestMapping(value="/generate/{path}")
public class TestController {
#Autowired
private ApplicationContext applicationContext;
#RequestMapping(method = RequestMethod.POST)
public String someHandlerMethod(#PathVariable String path) {
IService service = (IService) applicationContext.getBean(path + "Service");
IUserInput userInput = (IUserInput) applicationContext.getBean(path + "UserInput");
// Logic using path specific IService and IUserInput
}
}
I'm new to Java EE 6 so I apologize if the answer to this question is obvious. I have a task that must run hourly to rebuild a Solr index from a database. I also want the rebuild to occur when the app is deployed. My gut instinct is that this should work:
#Singleton
#Startup
public class Rebuilder {
#Inject private ProposalDao proposalDao;
#Inject private SolrServer solrServer;
#Schedule(hour="*", minute="0", second="0")
public void rebuildIndex() {
// do the rebuild here
}
}
Since I'm using myBatis, I have written this producer:
public class ProposalSessionProvider {
private static final String CONFIGURATION_FILE = "...";
static {
try {
sessFactory = new SqlSessionFactoryBuilder().build(
Resources.getResourceAsReader(CONFIGURATION_FILE));
}
catch (IOException ex) {
throw new RuntimeException("Error configuring MyBatis: " + ex.getMessage(), ex);
}
}
#Produces
public ProposalsDao openSession() {
log.info("Connecting to the database");
session = sessFactory.openSession();
return session.getMapper(ProposalsDao.class);
}
}
So I have three concerns:
What's the appropriate way to trigger a rebuild at deployment time? A #PostConstruct method?
Who is responsible for closing the database connection, and how should that happen? I'm using myBatis which is, I believe, pretty ignorant of the Java EE lifecycle. It seems like if I use #Singleton the connections will never be released, but is it even meaningful to put #Startup on a #Stateless bean?
Should the Rebuilder be a singleton or not? It seems like if it is not I couldn't use #PostConstruct to handle the initial rebuild or I'll get double rebuilds every hour.
I'm not really sure how to proceed here. Thanks for your time.
I don't know myBatis but i can tell you than #Schedule job is transactional. Anyway i'am not sure that JTA managed transaction will apply here according to the way you retrieve the session. Isn't there a way to retrieve a persistenceContext in MyBatis ? For the trigger part IMHO #Startup will do the job properly and will need a singleton bean so. Anyway i'am not able to tell you which of the 2 methods you propose is the best one.
For the scheduling part, you are correct; I'd write the index building logic in a separate class, and have both a (Singleton?) #StartUp bean and a #Schedule-annotated method in a separate class call it.
JMS could be used by said beans to trigger the index rebuilding, if you don't want to have a dependency between the index-building code, and the triggering code in said classes.
I don't know myBatis well enough, but if your connection is managed by a data source #Resource, then I believe it could indeed benefit from CMT.