I am developing an app in spring 4.1 . I know that Controllers / any other bean in spring are not thread safe . ie: Singleton. That mean same instance of Controller will be used to process multiple concurrent requests. Till here I am clear . I want to confirm that do I need to explicitly set #Scope("prototype") or request in the Controller class ? I read on StackOverflow previous post that even if scope is not set as request/prototype , Spring container will be able to process each request individually based on #RequestParams passed or #ModelAttribute associated with method arguements .
So i want to confirm is my below code is safe to handle multiple request concurrently ?
#Controller
public class LogonController {
/** Logger for this class and subclasses */
protected final Log logger = LogFactory.getLog(getClass());
#Autowired
SimpleProductManager productManager;
#Autowired
LoginValidator validator;
#RequestMapping( "logon")
public String renderForm(#ModelAttribute("employee") Logon employeeVO)
{
return "logon";
}
#RequestMapping(value="Welcome", method = RequestMethod.POST)
public ModelAndView submitForm(#ModelAttribute("employee") Logon employeeVO,
BindingResult result)
{
//Check validation errors
validator.validate(employeeVO, result);
if (result.hasErrors()) {
return new ModelAndView("logon");
}
if(!productManager.chkUserValidation(employeeVO.getUsername(), employeeVO.getPassword())){
return new ModelAndView("logon");
}
ModelAndView model = new ModelAndView("Welcome");
return model ;
}
}
Also i have another doubt.
since i am using SimpleProductManager productManager; Do i need to specify scope="prototype in its bean declaration in app-servlet.xml ?
Below is my configuration.xml
<bean id="mySessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="dataSource"><ref bean="dataSource"/></property>
<property name="configLocation" value="classpath:hibernate.cfg.xml" />
</bean>
<bean id="productManager" class="com.BlueClouds.service.SimpleProductManager" >
<property name="productDao" ref="productDao"/>
</bean>
<bean id="productDao" class="com.BlueClouds.dao.HbmProductDao">
<property name="sessionFactory"><ref bean="mySessionFactory"/></property>
</bean>
<bean id="loginValidator" class="com.BlueClouds.service.LoginValidator" >
</bean>
Being singleton single instance of validator is being shared among all request , for that do i need to add scope=request in bean configuration xml or do i need to surround validate() in synchronized block ? Please advise.
Thanks much .
You can tell your code is thread safe or not by answering following questions
Are there threads might modify a static field, which is not thread safe(ex: arrayList), in the same time?
Are there threads might modify a field of an instance, which is not thread safe, in the same time?
If any answer of the above is yes, then your code is not thread safe.
Since your code doesn't change any field, so it should be thread safe.
The general idea about thread safe is that if there are threads might change/access the same memory section in the same time, then it's not thread safe, which means "synchronized" is needed.
You'd better learn more about stack memory, heap memory and global memory in JAVA. So that you can understand if your code changes the same memory section in the same time or not.
Related
I have a compositeItemProcessor as below
<bean id="compositeItemProcessor" class="org.springframework.batch.item.support.CompositeItemProcessor">
<property name="delegates">
<list>
<bean class="com.example.itemProcessor1"/>
<bean class="com.example.itemProcessor2"/>
<bean class="com.example.itemProcessor3"/>
<bean class="com.example.itemProcessor4"/>
</list>
</property>
</bean>
The issue i have is that within itemProcessor4 i require values from both itemProcessor1 and itemProcessor3.
I have looked at using the Step Execution Context but this does not work as this is within one step. I have also looked at using #AfterProcess within ItemProcessor1 but this does not work as it isn't called until after ItemProcessor4.
What is the correct way to share data between delegates in a compositeItemProcessor?
Is a solution of using util:map that is updated in itemProcessor1 and read in itemProcessor4 under the circumstances that the commit-interval is set to 1?
Using the step execution context won't work as it is persisted at chunk boundary, so it can't be shared between processors within the same chunk.
AfterProcess is called after the registered item processor, which is the composite processor in your case (so after ItemProcessor4). This won't work neither.
The only option left is to use some data holder object that you share between item processors.
Hope this helps.
This page seems to state that there are two types of ExecutionContexts, one at step-level, one at job-level.
https://docs.spring.io/spring-batch/trunk/reference/html/patterns.html#passingDataToFutureSteps
You should be able to get the job context and set keys on that, from the step context
I had a similar requirement in my application too. I went with creating a data transfer object ItemProcessorDto which will be shared by all the ItemProcessors. You can store data in this DTO object in first processor and all the remaining processors will get the information out of this DTO object. In addition to that any ItemProcessor could update or retrieve the data out of the DTO.
Below is a code snippet:
#Bean
public ItemProcessor1<ItemProcessorDto> itemProcessor1() {
log.info("Generating ItemProcessor1");
return new ItemProcessor1();
}
#Bean
public ItemProcessor2<ItemProcessorDto> itemProcessor2() {
log.info("Generating ItemProcessor2");
return new ItemProcessor2();
}
#Bean
public ItemProcessor3<ItemProcessorDto> itemProcessor3() {
log.info("Generating ItemProcessor3");
return new ItemProcessor3();
}
#Bean
public ItemProcessor4<ItemProcessorDto> itemProcessor4() {
log.info("Generating ItemProcessor4");
return new ItemProcessor4();
}
#Bean
#StepScope
public CompositeItemProcessor<ItemProcessorDto> compositeItemProcessor() {
log.info("Generating CompositeItemProcessor");
CompositeItemProcessor<ItemProcessorDto> compositeItemProcessor = new CompositeItemProcessor<>();
compositeItemProcessor.setDelegates(Arrays.asList(itemProcessor1(), itemProcessor2(), itemProcessor3), itemProcessor4()));
return compositeItemProcessor;
}
#Data
public class ItemProcessorDto {
private List<String> sharedData_1;
private Map<String, String> sharedData_2;
}
I'm trying a very straightforward thing - catching the MaxUploadSizeExceededException errors associated with file uploads.
Here's the relevant bit in my spring-servlet.xml :
<bean id="multipartResolver"
class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<property name="maxUploadSize" value="100000" />
</bean>
And here's the #ExceptionHandler method in the controller that also handles the file upload stuff
#ExceptionHandler(MaxUploadSizeExceededException.class)
public String handleException(MaxUploadSizeExceededException e, RedirectAttributes redirectAttributes) {
redirectAttributes.addFlashAttribute("uploadErrorMessage", e.getCause().getMessage());
return "redirect:/page";
}
File upload is working fine. However, when I test with a file that exceeds the size limit - it throws the error, and the method for ExceptionHanler is never called.
Any help or pointers on what else to look for / at would be greatly appreciated.
Can you try changing the ExceptionHandler to look for LimitExceededException and MultiPartException instead of the sub Exceptions?
Try creating a separate class with #ControllerAdvice this will then take care of exception coming from all controllers.
#ControllerAdvice
public class ExceptionControllerAdvice {
#ExceptionHandler(MaxUploadSizeExceededException.class)
public String handleException(MaxUploadSizeExceededException e, RedirectAttributes redirectAttributes) {
redirectAttributes.addFlashAttribute("uploadErrorMessage", e.getCause().getMessage());
return "redirect:/page";
}
}
Thus if we define our #ExceptionHandler annotation on method in #ControllerAdvice class, it will be applied to all the controllers.
You must define following in your spring-servlet.xml file.
<mvc:annotation-driven/>
We are using Struts2-Spring integration and all my action classes implement SessionAware, sample code to action class and their spring definition is given below,
public class IRXxxxAction extends ActionSupport implements SessionAware {
private Map session;
public String execute()
{//}
public void setSession(Map<String, Object> session)
{
this.session = session;
}
}
Spring Configuration
<bean name="userAction" class="com.IRXxxxAction" >
<property name="adminDAO" ref="adminDAO" />
</bean>
If I understand correctly, each auto-wired property will be a singleton, so if the above is true, is there anyway that the session map get shared between two simultaneous requests?
Regards,
Ayush
You have asked same question on the user mailing list and as said if you are using Struts2-Spring plugin make sure to put bean scope as prototype.
Struts2 create new instance of action on each request, since action work as a model also and in order to make it thread safe a new object is being created on each request and placed on value stack.
Not proving scope will be treated by Spring as singleton and for ever request same action instance will be given back which can leads to a lot of issue from data corruption to weird behavior.
I have a Spring mvc (3.1.1) app, and I want to define conditions beyond what's available in RequestMapping. I have a couple of things I want to use it for.
First, it would be nice if I could show a different home page for different user types:
#Controller
public class HomepageController {
#RequestMapping(value = "/")
#CustomCondition(roles = Guest.class)
public String guestHome() { /*...*/ }
#RequestMapping(value = "/")
#CustomCondition(roles = Admin.class)
public String adminHome() { /*...*/ }
}
Second, I want the app to function both as a web site and as a REST service (e.g. for mobile apps), so I'd want to let the website access both html and json actions, and let the service (different subdomain) only access json actions (some kind of #CustomCondition(web = true) which only matches website urls)
Can this work for any of the two uses I'm planning?
I found very little documentation about custom conditions, but I did find one example that implements custom conditions which might be what I want, but it uses a #Configuration class instead of the XML configuration which I'm using and I don't want to move my entire spring xml definitions to a #Configuration class.
Can I define a customMethodCondition for RequestMappingHandlerMapping in the XML?
I tried subclassing RequestMappingHandlerMapping and override getCustomMethodCondition, to return my custom RequestCondition, but it didn't work - getMatchingCondition() in my condition didn't fire.
Any help would be greatly appreciated!
UPDATE
I read a little more, and it looks like RequestMappingHandlerMapping is a new class (since ver 3.1).
What happens in my app is that the #Configuration that tries to override and thereby redefine the requestMappingHandlerMapping bean actually works, but the url mappings (#RequestMapping methods in #Controllers) seem to get processed twice, once by the subclass ExtendedRequestMappingHandlerMapping and once by the original RequestMappingHandlerMapping --first with a custom condition, and then again without it.
Bottom line is my custom conditions are simply ignored.
This is supposed to be an advanced pattern, but IMO it should be quite common...
Comments anyone?
Spring MVC already provides a mechanism for distinguishing between json and html, the RequestMapping annotation takes a consumes attribute which looks at the content type of the request...
// REST version, Content-type is "application/json"
#RequestMapping(value = "/", consumes = "application/json")
public void myRestService() {
...
// HTML version, Content-type is not "application/json"
#RequestMapping(value = "/", consumes = "!application/json")
public void myHtmlService() {
...
Another way to use the same url but have distinct methods is with the param or headers attribute...
// the url is /?role=guest
#RequestMapping(value = "/", param = "role=guest")
public void guestService() {
// the url is / with header role=admin
#RequestMapping(value = "/", headers = "role=admin")
public void adminService() {
I would think you would want distinct urls for security. Typically, with something like Spring Security, you would put all of the admin functionality under /admin and let the framework manage it all...
<http auto-config="true">
<intercept-url pattern="/admin/**" access="ROLE_ADMIN" />
...
Would this be sufficient for your use case(s)?
If you have extended RequestMappingHandlerMapping(say ExtendedRequestMappingHandlerMapping) you have to register this new mapping a little differently in application context xml.
You cannot use <mvc:annotation-driven/> to configure the Spring MVC as that defines it's own handlerMapping internally, you can instead do something along these lines(or follow the approach in the link with #Configuration that you have provided):
<bean name="handlerAdapter" class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
<property name="webBindingInitializer">
<bean class="org.springframework.web.bind.support.ConfigurableWebBindingInitializer">
<property name="conversionService" ref="conversionService"></property>
<property name="validator">
<bean class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean"/>
</property>
</bean>
</property>
<property name="messageConverters">
<list>
<bean class="org.springframework.http.converter.ByteArrayHttpMessageConverter"></bean>
<bean class="org.springframework.http.converter.StringHttpMessageConverter"></bean>
<bean class="org.springframework.http.converter.ResourceHttpMessageConverter"></bean>
<bean class="org.springframework.http.converter.xml.SourceHttpMessageConverter"></bean>
<bean class="org.springframework.http.converter.xml.XmlAwareFormHttpMessageConverter"></bean>
<bean class="org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter"></bean>
<bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"></bean>
</list>
</property>
</bean>
<bean name="handlerMapping" class="..ExtendedRequestMappingHandlerMapping">
</bean>
This should ensure that your mapping takes effect and will ensure that the appropriate handler method is found by the handlerAdapter component.
Is it possible to create a factory or proxy that can decide if thread is running in (Web)Request or background-process (ie. scheduler) and then depending on that information, it creates a session bean or a prototype bean?
Example (pseudo Spring config :)
<bean id="userInfoSession" scope="session" />
<bean id="userInfoStatic" scope="prototype" />
<bean id="currentUserInfoFactory" />
<bean id="someService" class="...">
<property name="userInfo" ref="currentUserInfoFactory.getCurrentUserInfo()" />
</bean>
I hope this makes my question easier to understand...
My Solution
It's never to late to update own questions ;). I solved it with two different instances of client session, one SessionScoped client session and one SingletonScoped session. Both are normal beans.
<bean id="sessionScopedClientSession" class="com.company.product.session.SessionScopedClientSession" scope="session">
<aop:scoped-proxy />
</bean>
<bean id="singletonScopedClientSession" class="com.company.product.session.SingletonScopedClientSession" />
<bean id="clientSession" class="com.company.product.session.ClientSession">
<property name="sessionScopedClientSessionBeanName" value="sessionScopedClientSession" />
<property name="singletonScopedClientSessionBeanName" value="singletonScopedClientSession" />
</bean>
The ClientSession will then decide if singleton or session scope:
private IClientSession getSessionAwareClientData() {
String beanName = (isInSessionContext() ? sessionScopedClientSessionBeanName : singletonScopedClientSessionBeanName);
return (IClientSession) ApplicationContextProvider.getApplicationContext().getBean(beanName);
}
Where session type could be gathered through this:
private boolean isInSessionContext() {
return RequestContextHolder.getRequestAttributes() != null;
}
All the classes implement a interface called IClientSession. Both singletonScoped and sessionScoped beans extends from a BaseClientSession where the implementation is found.
Every service then can use the client session ie:
#Resource
private ClientSession clientSession;
...
public void doSomething() {
Long orgId = clientSession.getSomethingFromSession();
}
Now if we go one step further we can write something like a Emulator for the session. This could be done by initializing the clientSession (which is in no context of a request) the singleton session. Now all services can use the same clientSession and we still can "emulate" a user ie:
clientSessionEmulator.startEmulateUser( testUser );
try {
service.doSomething();
} finally {
clientSessionEmulator.stopEmulation();
}
One more advice: take care about threading in SingletonScoped clientSession instance! Wouw, I thought I could do it with less lines ;) If you like to know more about this approach feel free to contact me.
I created small universal workaround to inject beans depends on context.
Guess we have two beans:
<bean class="xyz.UserInfo" id="userInfo" scope="session" />
<bean class="xyz.UserInfo" id="userInfoSessionLess" />
We want to use "userInfo" bean for web user actions and "userInfoSessionLess" bean for background services for example.
Wa also want to write code and don't want to think about context, for example:
#Autowired
//You will get "java.lang.IllegalStateException: No thread-bound request found: Are you referring to request attributes outside of an actual web request?" for session less services.
//We can fix it and autowire "userInfo" or "userInfoSessionLess" depends on context...
private UserInfo userInfo;
public save(Document superSecureDocument) {
...
superSecureDocument.lastModifier = userInfo.getUser();
...
}
Now we need create custom session scope to make it worked:
public class MYSessionScope extends SessionScope implements ApplicationContextAware {
private static final String SESSION_LESS_POSTFIX = "SessionLess";
private ApplicationContext applicationContext;
public Object get(String name, ObjectFactory objectFactory) {
if (isInSessionContext()) {
log.debug("Return session Bean... name = " + name);
return super.get(name, objectFactory);
} else {
log.debug("Trying to access session Bean outside of Request Context... name = " + name + " return bean with name = " + name + SESSION_LESS_POSTFIX);
return applicationContext.getBean(name.replace("scopedTarget.", "") + SESSION_LESS_POSTFIX);
}
}
private boolean isInSessionContext() {
return RequestContextHolder.getRequestAttributes() != null;
}
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
}
Register new scope:
<bean class="org.springframework.beans.factory.config.CustomScopeConfigurer">
<property name="scopes">
<map>
<entry key="mySession">
<bean class="com.galantis.gbf.web.MYSessionScope" />
</entry>
</map>
</property>
</bean>
Now we need modify beans definions like this:
<bean class="xyz.UserInfo" id="userInfo" scope="mySession" autowire-candidate="true"/>
<bean class="xyz.UserInfo" id="userInfoSessionLess" autowire-candidate="false"/>
That's all. Bean with name "SessionLess" will be used for all "mySession" scoped beans if we use bean outside of actual web request thread.
Your rephrase is indeed considerably simpler :)
Your currentUserInfoFactory could make use of RequestContextHolder.getRequestAttributes(). If a session is present and associated with the calling thread, then this will return a non-null object, and you can then safely retrieve the session-scoped bean from the context. If it returns a null, then you should fetch the prototype-scoped bean instead.
It's not very neat, but it's simple, and should work.
Create two custom context loaders that bind the same scope defintion to different implementations:
public final class SessionScopeContextLoader extends GenericXmlContextLoader {
protected void customizeContext(final GenericApplicationContext context) {
final SessionScope testSessionScope = new SessionScope();
context.getBeanFactory().registerScope("superscope", testSessionScope);
}
...
}
Then you make a corresponding one for singleton (make your own scope with just statics)
Then you just specify the appropriate context loader in the xml startup for each of the two contexts.