I have requirement for spring mvc 3 caching. Requirement is : while starting the server, we need to call database for one dropdown and put those values in the cache. So that whenever we required those values, we need to retrieve from cache.
Please help me with an example.
Thanks in advance.
May be you can use init-method (Spring 2.5) or #PostConstruct annotation (in Spring 3.0).
This method will be called during server start up
The following is code snippet
#Component
public class CacheDBData {
private String values[];
//add setter & getter
//This will be called during server start up after properties are initialised
#PostConstruct
public void getDataFromDB() {
values = //Logic to get data from DB and store that in values property
}
}
Suppose for example you can use in class as follows
#controller
public class HomeController {
#Autowired
private CacheDBData cacheDBData ;
//getter and setters
private void methodxyz() {
String values[] = cacheDBData.getValues();
}
}
I've had success with Ehcahe for Spring. There's a couple of config files to setup but after that you simply annotate the methods you want to cache the output from and it just works.
This has the advantage that you can change the values coming back from the service/database and NOT have to restart your app, unlike the accepted answer.
Related
I'm going to use #InsertOnlyProperty with Spring Boot 2.7 as it will take time for us to migrate to Spring Boot 3.0!
So I'm going to create my DataAccessStrategy based on the DefaultAccessStrategy and also override the SqlParametersFactory so that I can pass the RelationalPersistentProperty::isInsertOnly condition to the getParameterSource method, also overriding RelationalPersistentProperty by adding isInsertOnly. And is there a way to override RelationalPersistentProperty to add isInsertOnly property. Am I correct or is there a better solution than switching to Spring Boot 3.0 now. Thank you!
Since #InsertOnlyProperty is only supported for the aggregate root (in Spring Boot 3.0), one approach could be to copy the data to a surrogate object and use a custom method to save it. It would look something like this:
public record MyAggRoot(#Id Long id,
/* #InsertOnlyProperty */ Instant createdAt, int otherField) {}
public interface MyAggRootRepository
extends Repository<MyAggRoot, Long>, MyAggRootRepositoryCustom { /* ... */ }
public interface MyAggRootRepositoryCustom {
MyAggRoot save(MyAggRoot aggRoot);
}
#Component
public class MyAggRootRepositoryCustomImpl implements TaskRepositoryCustom {
#Autowired
private final JdbcAggregateOperations jao;
// Override table name which would otherwise be derived from the class name
#Table("my_agg_root")
private record MyAggRootForUpdate(#Id Long id, int otherField) {}
#Override
public MyAggRoot save(MyAggRoot aggRoot) {
// If this is a new instance, insert as-is
if (aggRoot.id() == null) return jao.save(aggRoot);
// Create a copy without the insert-only field
var copy = new MyAggRootForUpdate(aggRoot.id(), aggRoot.otherField());
jao.update(copy);
return aggRoot;
}
}
It is however a bit verbose so it would only be a reasonable solution if you only need it in a few places.
I have some data objects that are common across a Spring boot application - one is the logged in employee object and other is a category. I have created a #Component class which contains these are static variables. This way I do not even have to autowire them. They can be used directly like CurrentContext.employee in controllers.
#Component
public final class CurrentContext {
public static Category currentCategory;
public static Employee employee;
#Autowired
private CategoryService categoryService;
#Autowired
private EmployeeService employeeService;
#EventListener
public void onApplicationEvent(ContextRefreshedEvent event) {
currentCategory = categoryService.getCategory();
}
#EventListener
public void onLoginSuccess(InteractiveAuthenticationSuccessEvent event) {
employee = employeeService.getEmployeeByUserId(((MyUserDetails) event.getAuthentication().getPrincipal()).getUserId());
}
}
Is this a right way? Please suggest if there is a better way to handle shared data
Edit
Some background - I require the current logged in employee and a category which is common for all employees. So I autowired employeeService and categoryService in my controllers and use them to get the data. They are required in almost all my controller methods, so, I wanted to create a bean of these so that I directly use them in my controller and also save frequent database calls.
Normally, we only put the dependencies related to the cross-cutting concerns (i.e dependencies that are across the whole application such as security , logging , transaction stuff , time provider etc.) in the static field.
By accessing these kind of dependencies in the static way , we don't need to pass them through method parameters /constructors from object to object , which will make the API much cleaner without such noise (BTW. This is called Ambient Context Pattern in the .NET world).
Your Employee object most probably belong to this type , so it is ok to access it in a static way. But as their scope is per session , you cannot simply put it in the static field of a class. If yes, then you always get the same employee for all sessions. Instead, you have to somehow store it in an object which is session scope (e.g HttpSession) . Then at the beginning of handling a web request , you get it from the session and then put it in a ThreadLocal which is encapsulated inside a "ContextHolder" object. You then access that "ContextHolder" in a static way.
Sound very complicated and scary ? Don't worry as Spring Security has already implemented this stuff for you. What you need to do is to customize Authentication#getPrincipal()or extend default Authentication to contain your Employee. Then get it using SecurityContextHolder.getContext().getAuthentication()
For your currentCategory , if they are not the cross-cutting concerns and is the application scope , make a singleton bean to get it values is a much better OOP design.
#Component
public final class CurrentCategoryProvider {
#Autowired
private CategoryService categoryService;
public Category getCurrentCategory(){
//or cache the value to the an internal properties depending on your requirements
return categoryService.getCategory();
}
}
You then inject CurrentCategoryProvider to the bean that need to access currentCategory.
I want to add a property in application.properties of my spring boot application and be able to to access it and use it in one of my other classes, but I am getting null.
Here is my application.properties
server.port=8052
subscribe.period=5
My class that will access it
#Component
public class SubscriptionService {
#Value("${subscribe.period}")
private String period
#Autowired
public SubscriptionService(String period) {
String time = period;
...
}
}
But it seems period is not being populated, in fact null. It shows as nill when I run as maven build in eclipse at least, im thinking it might be trying to access it before the properties file is even load, if so how might i approach this?
Deinum in the comments above is correct. I have no idea why as it differs from every other online example I have read so I would invite him to give an explanation.
I had to put the #Value in the argument of the constructor
#Component
public class SubscriptionService {
private String period
#Autowired
public SubscriptionService(#Value("${subscribe.period}") String period) {
String time = period;
...
}
}
Then it works
I have Spring 4.1 Application. I am trying to schedule based on value from property file. I have read this post. But I do not want the following way of EL inside #Scheduled
#Scheduled(fixedDelayString = "${my.fixed.delay.prop}")
public void readLog() {
...
}
Here is my class.
public class MyService {
#Value("${timerInMilliSeconds: 60000}")
private long timerinMilliSeconds;
public myService(){
}
#Scheduled(fixedRate = timerinMilliSeconds)
public void myTimer() {
//do stuff
}
}
I get this error.
The value for annotation attribute Scheduled.fixedRate must be a constant
expression
You can't do that; it's a limitation of the way annotations work - Strings in annotations have to be constants (they are stored in the class and can't be different for each instance).
By the way ${my.fixed.delay.prop} is not "EL", it's a property placeholder.
I am using spring jpa transactions in my project.One Case includes inserting a data in a synchronized method and when another thread accesses it the data is not updated.My code is given below :
public UpdatedDTO parentMethod(){
private UpdatedDTO updatedDTO = getSomeMethod();
childmethod1(inputVal);
return updatedDTO;
}
#Transactional
public synchronized childmethod1(inputVal){
//SomeCodes
//Place where update takes place
TableEntityObject obj = objectRepository.findByInputVal(inputVal);
if(obj == null){
childMethod2(inputVal);
}
}
#Transactional
public void childMethod2(inputVal){
//Code for inserting
TableEntityObject obj = new TableEntityObject();
obj.setName("SomeValue");
obj.setValueSet(inputVal);
objectRepository.save(obj);
}
Now if two threads access at the same time and if first thread completes childmethod2 and childmethod1 and without completing parentMethod() after that if second thread comes to the childMethod1() and checks if data exists,the data is null and is not updated by first thread.I have tried many ways like
#Transactional(propagation = Propagation.REQUIRES_NEW)
public synchronized childmethod1(inputVal){
//SomeCodes
//Place where update takes place
TableEntityObject obj = objectRepository.findByInputVal(inputVal);
if(obj == null){
childMethod2(inputVal);
}
}
#Transactional(propagation = Propagation.REQUIRES_NEW)
public void childMethod2(inputVal){
//Code for inserting
TableEntityObject obj = new TableEntityObject();
obj.setName("SomeValue");
obj.setValueSet(inputVal);
objectRepository.save(obj);
}
also tried taking off #transactional in the childMethod1() but nothing works out.I know im doing something wrong here , but couldnt figure out where and what exactly i am doing wrong.Can anyone help me out with this
#Transactional is resolved using proxies on spring beans. It means it will have no effect if your method with #Transactional is called from the same class. Take a look at Spring #Transaction method call by the method within the same class, does not work?
The easiest would be moving those methods into separate service.
Typical checklist I follow in cases like these :
If Java based configuration then make sure
#EnableTransactionManagement annocation is present in the class
containing the #Configuration annotation
Make sure the transactionManager bean is created, again this should be mentioned in the configuration class.
Use of #Transactional annocatio over the method which is calling the repository, typically a class in the DAO layer
Adding the #Service annotation for the class which is invoking the methods in the repository
Nice blog which explains the Transaction configuration with JPA in depth --> http://www.baeldung.com/2011/12/26/transaction-configuration-with-jpa-and-spring-3-1/68954