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JAVA Spring Boot : How to access application.properties values in normal class

I know how I can access the application.properties values in #Service classes in Java Spring boot like below
#Service
public class AmazonClient {
#Value("${cloud.aws.endpointUrl}")
private String endpointUrl;
}
But I am looking for an option to access this value directly in any class (a class without #Service annotation)
e.g.
public class AppUtils {
#Value("${cloud.aws.endpointUrl}")
private String endpointUrl;
}
But this returns null. Any help would be appreciated.
I have already read here but didn't help.

There's no "magic" way to inject values from a property file into a class that isn't a bean. You can define a static java.util.Properties field in the class, load values from the file manually when the class is loading and then work with this field:
public final class AppUtils {
private static final Properties properties;
static {
properties = new Properties();
try {
ClassLoader classLoader = AppUtils.class.getClassLoader();
InputStream applicationPropertiesStream = classLoader.getResourceAsStream("application.properties");
applicationProperties.load(applicationPropertiesStream);
} catch (Exception e) {
// process the exception
}
}
}

You can easily achievw this by annotating ur app utils class with #component annotation . spring will take care of loading properties.
But if you don't want to do that approach , then look at the link below .
https://www.baeldung.com/inject-properties-value-non-spring-class

Spring use different property files depending on request params

Background:
I am working on a java Spring REST microservice that needs to work with multiple identical back-end systems and multiple identical databases depending on the request parameters.
Basically I have 3 "brands". For each brand there is a set of downstream services and a database. I have no control over those.
My spring service will receive brand as a part of request and will need to call the right downstream services and use the correct database.
Previously I would deal with this by having a separate instance of the spring service for each of the brands. There would be a single property file for each brand and spring would use it to wire up beans. I would have separate URL's for each brand and there was no problem.
Some of my beans need to know about "brand" during creation as they are wrappers around connections downstream services. I.e. once the bean is created there won't be a way to switch it to be a "different brand".
Problem:
I would like to change this so that a single instance of my service can handle requests for any brand.
Requirements:
I was thinking about the following solution:
Have a general property file for non-branded stuff. Spring would wire any non-branded beans and keep them as singleton beans.
Have a property file with brand specific urls etc for each of the brands
Spring would create set of singleton beans for each of the brand using appropriate property file.
Next when the request comes in spring would read the request params and use bean specific for that brand.
Performance is important to me so I would like to reuse the beans as much as possible.
I would like to make this thing as transparent as possible so that people creating new beans don't have to worry about doing anything outside standard configuration/context class.
Does anyone know what would be the best solution to achieve this?

I think you can solve the problem injecting the service in every request with the right set of configurations and beans; possibly already existing in your Application Context.
Given:
$ curl http://localhost:8080/greetings/rodo && echo
Hi from brand1, rodo
$ curl -H "x-brand-name: brand1" http://localhost:8080/greetings/rodo
Hi from brand1, rodo
$ curl -H "x-brand-name: brand2" http://localhost:8080/greetings/rodo && echo
Hi from brand2, rodo
The following code would work:
-- application.yml --
brand1:
greetingPrefix: Hi from brand1,
brand2:
greetingPrefix: Hi from brand2,
-- DemoApplication.java --
#SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
#Configuration
class ServiceConfig {
#Bean
public GreetingService greetingServiceBrand1(Brand1Config config) {
return new GreetingService(config);
}
#Bean
public GreetingService greetingServiceBrand2(Brand2Config config) {
return new GreetingService(config);
}
}
#Configuration
class WebConfig implements WebMvcConfigurer {
#Autowired
private ApplicationContext applicationContext;
#Override
public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
resolvers.add(greetingServiceResolver());
}
private GreetingServiceResolver greetingServiceResolver() {
GreetingService greetingServiceBrand1 = applicationContext.getBean("greetingServiceBrand1", GreetingService.class);
GreetingService greetingServiceBrand2 = applicationContext.getBean("greetingServiceBrand2", GreetingService.class);
return new GreetingServiceResolver(greetingServiceBrand1, greetingServiceBrand2);
}
}
}
#RestController
#RequestMapping("/greetings")
class GreetingController {
#GetMapping("/{name}")
public String get(GreetingService greetingService, #PathVariable String name) {
return greetingService.sayHi(name);
}
}
class GreetingServiceResolver implements HandlerMethodArgumentResolver {
private final GreetingService greetingServiceBrand1;
private final GreetingService greetingServiceBrand2;
public GreetingServiceResolver(GreetingService greetingServiceBrand1, GreetingService greetingServiceBrand2) {
this.greetingServiceBrand1 = greetingServiceBrand1;
this.greetingServiceBrand2 = greetingServiceBrand2;
}
#Override
public boolean supportsParameter(MethodParameter parameter) {
return parameter.getParameterType().equals(GreetingService.class);
}
#Override
public Object resolveArgument(
MethodParameter methodParameter,
ModelAndViewContainer modelAndViewContainer,
NativeWebRequest nativeWebRequest,
WebDataBinderFactory webDataBinderFactory
) throws Exception {
String brand = nativeWebRequest.getHeader("x-brand-name");
return resolveGreetingService(brand);
}
private GreetingService resolveGreetingService(String brand) {
if ("brand2".equals(brand)) {
return greetingServiceBrand2;
}
return greetingServiceBrand1; // default
}
}
class GreetingService {
private BaseConfig config;
public GreetingService(BaseConfig config) {
this.config = config;
}
public String sayHi(String name) {
return config.getGreetingPrefix() + " " + name;
}
}
abstract class BaseConfig {
private String greetingPrefix;
public String getGreetingPrefix() {
return greetingPrefix;
}
public void setGreetingPrefix(String greetingPrefix) {
this.greetingPrefix = greetingPrefix;
}
}
#Configuration
#ConfigurationProperties("brand1")
class Brand1Config extends BaseConfig {
}
#Configuration
#ConfigurationProperties("brand2")
class Brand2Config extends BaseConfig {
}
As you can see, it's fundamental to pass the service to each controller method, write a resolver and inject the right set of dependencies depending on a parameter passed to the request, in this case via header.

Since your property files need to be declared statically anyway, you can just write all your different brand stuff in the same property file, like in a key-value format, that Spring can pick up as a list of configurations.
brandConfigs:
- brand: foo
property: foos
- brand2: bar
porperty: bars
Load all your connection beans to your downstream services on startup and just route to them according to your request param. Imo this seems to be the most straight forward and performant way. If some of these downstreams are used very rarely you can lazy load the beans on-demand, but probably this wouldn't make a sense unless you have thousands of different downstream routes.

How to create a dynamic proxy of a already proxyed class in spring

I'm relativly new to spring/spring boot.
At the moment I'm using a spring boot rest application which provides an FeignClient to be included in other projects. Now, I want those FeignClients be wrapped by a CircuitBreaker.
The best solution I came up with, is that I dynamically create a proxy which includes the CircuitBreaker implementation which itself calls the created FeignClient.
So let's assume I have the following interface which describes the RestController:
#RequestMapping("/")
public interface MyWebService {
#GetMapping("name")
public String getName();
}
Now, I have the interface for the FeignClient:
#FeignClient("app")
public interface WebServiceClient extends WebService {
}
So.. My goal would be to achieve something like I have another annotation e. g. #WithCircuitBreaker which I then will be scanned for and dynamically create a proxy bean which will be injected instead of the FeignClient bean.
At the moment my code looks like this:
#FeignClient("app")
#WithCircuitBreaker
public interface WebServiceClient extends WebService {
}
As far as I know, I can now create a #Configuration Class which will look like this:
#Configuration
public class WithCircuitBreakerConfiguration implements ImportAware {
private AnnotationMetadata annotationMetadata;
private AnnotationAttributes annotationAttributes;
#Override
public void setImportMetadata(AnnotationMetadata importMetadata) {
this.annotationMetadata = importMetadata;
Map<String, Object> annotatedClasses = importMetadata.getAnnotationAttributes(WithCircuitBreaker.class.getName());
this.annotationAttributes = AnnotationAttributes.fromMap(annotatedClasses);
}
What else to import to create the proxy and inject it?
}
Now I'm at the point, which I don't know how to continue. How to dynamically create a proxy class which does something like this:
public class PorxyedWebService {
private WebService feignClientProxy;
#Autowired
public ProxyedWebService(WebService feignClientProxy) {
this.feignClientProxy = feignClientProxy;
}
public String getName() {
...
<some circuitbreaker stuff>
....
return this.feignClientProxy.getName();
}
}
and then return this proxy instead of the proxy generated from Feign as soon as someone autowires the WebService interface.

I am not a Spring user, but I do know that Spring does not create proxies recursively if e.g. multiple Spring AOP aspects are applied to the same object. Instead, additional interceptors (or advices in AOP language) are registered upon the same proxy. I think you want to use that infrastructure in order to achieve whatever your objective is.

You can just use the resilience4j Spring Boot2 starter.
You can combine the #CircuitBreaker annotation with the #FeignClient annotation at interface level.
You can then use it as follows:
#FeignClient(name = DUMMY_FEIGN_CLIENT_NAME)
#CircuitBreaker(name = DUMMY_FEIGN_CLIENT_NAME)
public interface DummyFeignClient {
String DUMMY_FEIGN_CLIENT_NAME = "dummyFeignClient";
#GetMapping(path = "/api/{param}")
void doSomething(#PathVariable(name = "param") String param);
}

Dependency of one class on three interfaces Guice

I have the following application class which uses a server to run its logic
Implementation of the application class is as follows:
package edu.umd.fcmd.guice.application;
import com.google.inject.Guice;
import com.google.inject.Injector;
public class WebApplication {
private WebServer server;
public void run() {
System.out.println("starting web application...");
Injector injector = Guice.createInjector(new WebGuiceModule());
server = injector.getInstance(WebServer.class);
server.run();
System.out.println("web application finished.");
}
public static void main(String[] args) {
WebApplication app = new WebApplication();
app.run();
}
}
The server class is as follows which depends on three interfaces:
public class WebServer{
private final Frontend frontend;
private final Middleware middleware;
private final Persistance persistance;
#Inject
public WebServer(#Named("front")Frontend frontend, #Named("middle")Middleware middleware, #Named("pers")Persistance persistance) {
this.frontend = frontend;
this.middleware = middleware;
this.persistance = persistance;
}
public String getType() {
return "WebServer";
}
public boolean run() {
System.out.println("running " + this.getType());
Injector injector = Guice.createInjector();
Frontend frontend = injector.getInstance(Frontend.class);
frontend.run();
Middleware middleware = injector.getInstance(Middleware.class);
middleware.run();
Persistance persistance = injector.getInstance(Persistance.class);
persistance.run();
return true;
}
}
My webguicemodule is as follows:
public class WebGuiceModule extends AbstractModule{
#Override
protected void configure(){
bind(WebServer.class).annotatedWith(Names.named("front")).to(FrontEnd.class);
bind(WebServer.class).annotatedWith(Names.named("middle")).to(Middleware.class);
bind(WebServer.class).annotatedWith(Names.named("pers")).to(Persistance.class);
}
}
I am not sure why my module is not working properly. It is still in errors when I am writing the bind statements. Could not figure out why
I am receiving the following errors:
Exception in thread "main" java.lang.Error: Unresolved compilation problems:
The method to(Class<? extends WebServer>) in the type LinkedBindingBuilder<WebServer> is not applicable for the arguments (Class<FrontEnd>)
FrontEnd cannot be resolved to a type
The method to(Class<? extends WebServer>) in the type LinkedBindingBuilder<WebServer> is not applicable for the arguments (Class<Middleware>)
Middleware cannot be resolved to a type
The method to(Class<? extends WebServer>) in the type LinkedBindingBuilder<WebServer> is not applicable for the arguments (Class<Persistance>)
Persistance cannot be resolved to a type

You are not using bind() correctly. You've configured WebGuiceModule such that FrontEnd, Middleware, and Persistance are subclasses of WebServer. However, the compiler errors indicate that is not the case.
You just need to say:
bind(FrontEnd.class);
bind(Middleware.class);
bind(Persistance.class);
Then when you ask the injector for an instance of WebServer, it will know how to create the objects that it needs to pass into the constructor.
WebServer server = injector.getInstance(WebServer.class);
In this case, you don't need #Named. That is for a case like this:
public class Foo {
#Inject
public Foo(#Named("bar") Jar bar, #Named("tar") Jar tar) {
}
}
public interface Jar {}
public class Bar extends Jar {}
public class Tar extends Jar {}
Then in a module...
bind(Jar.class).annotatedWith(Names.named("bar")).to(Bar.class);
bind(Jar.class).annotatedWith(Names.named("tar")).to(Tar.class);
The "name" disambiguates which implementation of Jar to create and inject. Otherwise it wouldn't know, and it would error.

Thank you #JeremyHeiler. This Frontend interface happens to be in a different package. Now, Frontend is dependent on an interface called authentication. When I tried implementing it with the similar code as that of the webserver, I am getting errors. The code I wrote was the following:
package edu.umd.fcmd.guice.interfaces;
import com.google.inject.Guice;
import com.google.inject.Inject;
import com.google.inject.Injector;
import edu.umd.fcmd.guice.application.WebServer;
import edu.umd.fcmd.guice.interfaces.Authentication;
public interface Frontend{
private final Authentication authentication;
#Inject
public interface(Authentication authentication) {
System.out.println("5");
this.authentication = authentication;
}
public static String getType(){
return "Frontend";
}
public default boolean run(){
System.out.println("in frontend");
authentication.run();
return true;
}
}
Errors are the following:
Multiple markers at this line
- Duplicate field Frontend.authentication
- Illegal modifier for the interface field Frontend.authentication; only public, static & final are
permitted
Syntax error on token "interface", Identifier expected
The static field Frontend.authentication should be accessed in a static way
I have tried searching a lot on the internet but could not find figure out. I guess the problem is having files in different packages. If you could please let me know.

Why is my advice/pointcut not running at all?

Both 'aop:aspectj-autoproxy' and 'mvc:annotation-driven' are present in the XML config.
Both of these classes are defined as a bean inside of the same XML.
Using Spring 3.2.3.RELEASE and Google App Engine 1.8.1 in a local/dev environment.
My pointcut does not execute.
My advice. Declared inside a class annotated with #Aspect.
#Component
#Aspect
public class RequestLimiter {
private MemcacheService cache = MemcacheServiceFactory.getMemcacheService();
#Pointcut("within(#pcs.annotations.LimitRequests com.zdware.pcs.controllers.PingCollectorController)")
public void methodRequestLimited(){}
#Around("methodRequestLimited() && args(req,limitRequests)")
public Object requestGateWay(ProceedingJoinPoint jp, HttpServletRequest req,LimitRequests limitRequests) throws Throwable {
// do stuff
}
}
The method I am using to test in the controller layer.
#Controller
public class PingCollectorController {
#RequestMapping(value="/test")
#LimitRequests(requestTimeLimit = 1, functionName = "Test")
public String test(){
return "test"; // this will return me to a jsp that doesnt exist, but my advice is still not executing.
}
}

Is CGLIB in the classpath? It will be needed to generate the proxy (since your controller does not implement an interface, spring cannot use a simpler JDK proxy).