I wanted to play around with the different types of bean scopes. So I wrote a test environment which should generate a random number so I could see if a bean had changed. My test setup does not work and I can not explain what I found out.
I'm using Spring Boot 2.13 with the Spring Framework 5.15.
Following setup:
Main class:
package domain.webcreator;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
#SpringBootApplication
public class WebcreatorApplication {
public static void main(String[] args) {
SpringApplication.run(WebcreatorApplication.class, args);
}
}
Beans class:
package domain.webcreator;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import java.util.Random;
#Configuration
public class Beans {
#Bean
public Random randomGenerator() {
return new Random();
}
}
Scoper class:
package domain.webcreator;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Service;
import java.util.Random;
#Service
#Scope("singleton")
public class Scoper {
private Random rand;
public Scoper(Random rand) {
this.rand = rand;
}
public int getNumber(int max) {
return rand.nextInt(max);
}
}
Index Controller
package domain.webcreator.controller;
import domain.webcreator.Scoper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseBody;
#Controller
public class IndexController {
#GetMapping("/")
#ResponseBody
#Autowired
public String indexAction(Scoper scoper) {
return String.valueOf(scoper.getNumber(50));
}
}
My problem is, that I get an NPE while calling scoper.getNumber(50).
This is strange because when debugging, a Random bean is generated and passed to the scoper constructor.
Later on, in the controller, the rand property is null.
What am I doing wrong?
You're trying to apply #Autowired to a random method, which isn't how Spring works. Controller method parameters are for information specific to that HTTP request, not general dependencies, and so Spring is trying to create a new Scoper that is associated with the request--but it doesn't have any incoming values in the request to fill in. (I'm actually surprised you're not getting an error about no default constructor.)
Instead, pass your Scoper in a constructor.
#RestController
public class IndexController {
private final Scoper scoper;
public IndexController(Scoper scoper) {
this.scoper = scoper;
}
#GetMapping("/")
public String indexAction(Scoper scoper) {
return String.valueOf(scoper.getNumber(50));
}
}
A couple of notes:
Singleton scope is the default, and there's no need to specify it.
#RestController is preferable to repeating #ResponseBody unless you have a mixed controller class.
Related
Whenever I start a spring boot project I keep getting this error, This question has been asked multiple times on stakeoverflow I have tried all the solutions but nothing works for me. My first questions are what is the reason for this error, and how can I fix it.
FilterApplication.java
package com.example.filter;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
#SpringBootApplication()
public class FilterApplication {
public static void main(String[] args) {
SpringApplication.run(FilterApplication.class, args);
}
}
FilterConnector.java
package com.example.filter;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
#RestController
public class FilterConnector {
#Autowired
private FilterService filterService;
#GetMapping("/home")
public List<Filter> home()
{
return this.filterService.getData();
}
}
FilterService.java
package com.example.filter;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
#Service
public class FilterService {
#Autowired
private FilterDao filterDao;
public List<Filter> getData() {
System.out.println("----------------------HERE-------------");
return this.filterDao.findAll();
}
}
FilterDao.java
package com.example.filter;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
#Repository
public interface FilterDao extends JpaRepository<Filter, Integer> {
}
Spring framework relies on ApplicationContext to inject dependencies into the dependent object. For example your FilterDao will be inject into FilterService object.
To do this Spring will try to initialized instances of these classes at the start of the Application, but if it fails you will see this error message.
The problem with your code is related to FilterDao class, Spring can't initialize an instance of this class because it requires the Database to be configured correctly.
To fix this error:
you need to check your database connection is correct.
make sure there is a table corresponding to Filter class.
check the primary key (ID) is actually of type Integer.
If you provide full error stack I can give you a specific solution.
Note:
The issues is not related to FilterService or FilterConnector, because you are using #Autowired annotation implying the dependencies are optional and they will be injected after the bean initialization.
I am trying to make an application that uses Spring annotations to import the configurations. For this question i narrowed it down to two files. The Startup class:
package core;
import lombok.extern.slf4j.Slf4j;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
#Slf4j
#Configuration
#Import(ConfigSettings.class)
public class Startup {
public static void main (String args[]) {
log.info("main class");
}
}
and the ConfigSettings
package core;
import lombok.extern.slf4j.Slf4j;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
#Slf4j
#Configuration
#ComponentScan({"connections", "filter"})
#PropertySource({"classpath:config/${env.config:dev}.application.properties"})
public class ConfigSettings {
public ConfigSettings() {
log.info("Constructor ConfigSettings");
}
}
I expected the outcome to be:
[INFO]Constructor ConfigSettings
[INFO]main class
But it only shows mainclass. It looks like the constructor of the config settings is not called at all. I expect it to call it because of the import annotation.
Can anyone explain what is going wrong? Thank you in advance!
Your best bet is to make the config class return config object that contains your values. Generally I don't tend to add an all-encompassing config object, but have a config file for each component (database, controllers, etc...).
You can then return the configured object as a bean and let spring inject it. If I were to make a config file for a RestTemplate (as a simple example):
#Service
public class RestClientConfig {
#Value("${your.config.value}")
private String yourValue;
private final RestTemplate restTemplate = new RestTemplate();
#Bean
public RestTemplate restTemplate() {
// Configure it, using your imported values
// ...
return restTemplate;
}
}
However, the main method is outside of the spring container and you won't be able to bootstrap it that way, but with the above method you can call the configured component directly where you need to use it.
I'm working on Spring over Hibernate project an i'm only in the beginning.
I'm tryng to hav a SpringBootApplication which writes to MsSql some LogEntries objects.
I have some different packages:
here is the classes:
LogEntryFacadeImpl.class :
package com.tradingSystem.dataAccess;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import com.tradingSystem.entity.LogEntry;
#Service
public class LogEntryFacadeImpl implements LogEntryFacade{
#Autowired
private LogEntryDAO logEntryDao;
#Transactional
#Override
public Long addLogEntry(LogEntry log) {
return this.logEntryDao.save(log).getId();
}
#Override
public LogEntry getLogEntry(Long logId) {
return this.logEntryDao.findOne(logId);
}
}
LogEntryDAO.class:
package com.tradingSystem.dataAccess;
import org.springframework.data.jpa.repository.JpaRepository;
import com.tradingSystem.entity.LogEntry;
public interface LogEntryDAO extends JpaRepository<LogEntry, Long> {
}
and I use this class as tester:
TestApplication.class:
package com.testings;
import java.util.Date;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
import com.tradingSystem.dataAccess.LogEntryFacade;
import com.tradingSystem.entity.LogEntry;
#SpringBootApplication
#ComponentScan({"com.tradingSystem" })
public class TestApplication implements CommandLineRunner{
#Autowired
private LogEntryFacade logEntryFacade;
public static void main(String[] args) {
SpringApplication.run(TestApplication.class, args);
}
#Override
public void run(String... args) throws Exception {
LogEntry log = new LogEntry(552266, "Testing of log entry save",
new Date(System.currentTimeMillis()),
new Date(System.currentTimeMillis()));
System.err.println(log);
Long id = logEntryFacade.addLogEntry(log);
LogEntry log2 = logEntryFacade.getLogEntry(id);
System.err.println(log2);
}
}
wher i run this as application i get this message in console:
APPLICATION FAILED TO START
Description:
Field logEntryDao in com.tradingSystem.dataAccess.LogEntryFacadeImpl required a bean of type 'com.tradingSystem.dataAccess.LogEntryDAO' that could not be found.
Action:
Consider defining a bean of type 'com.tradingSystem.dataAccess.LogEntryDAO' in your configuration.
I put the #ComponentScan({"com.tradingSystem" }) annotation in the tester as you can see. however, still get this message.
(when I didnt use any packages separation, everything works fine...)
Please help me solve this
Thanks
You should add #Repository annotation above your Repository interface.
Optionally you can add it like #Repository(value="logEntryRepository")
the default scan path is package of #SpringBootApplication class, so you must declare three scan path, but it's seems like that you missing two scan config, you need add
#EnableJpaRepositories(basePackages = "com.tradingSystem.dataAccess")
#EntityScan(basePackages = "com.tradingSystem.entity")
#ComponentScan(basePackages = "com.tradingSystem.dataAccess")
to the TestApplication class
I am learning spring the from book the "Spring in Action fourth edition" by Craig Walls. I am trying to apply advice to the method declared by the interface and I am getting Exception. When I apply the same advice to the class which doesn't implement anything, everything works fine.
Spring version - 4.3.2
Help would be appreciated.
Exception:
Exception in thread "main"org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.fifczan.bean.UserService] is defined
Code:
Interface:
package com.fifczan.bean;
public interface Service {
void doTask();
}
Implementation:
package com.fifczan.bean;
import org.springframework.stereotype.Component;
#Component
public class UserService implements Service {
public void doTask() {
System.out.println("doing task");
}
}
Aspect:
package com.fifczan;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.stereotype.Component;
#Aspect
#Component
public class UserAspect {
//If i change Service(interface) to UserService(implementation)
//in pointcut I am getting the same exception
#Before("execution(* com.fifczan.bean.Service.doTask(..))")
public void userAdvice(){
System.out.println("doing sth before method doTask");
}
}
Configuration:
package com.fifczan;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;
#Configuration
#EnableAspectJAutoProxy
#ComponentScan
public class AspectJAutoProxyConfig {
}
main :
package com.fifczan;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import com.fifczan.bean.UserService;
public class AspectJAutoProxyTest {
public static void main(String[] args) {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(AspectJAutoProxyConfig.class);
UserService userService= ctx.getBean(UserService.class);
userService.doTask();
}
}
You're asking for a bean of UserService, which is the concrete class, not the interface. Retrieve or inject a bean of type Service.
I try to improve my Spring knowledge by reading Spring in action 4.
When I've to to section, describing using of Qualifier annotation (3.3.2), i faced the problem.
To test this annotation in action, I wrote Dessert interface, which is implemented by 3 classes, creating in context using #Component annotation.
I also created class Taster, which "tastes" some dessert, autowired into by some qualifier.
When I run my application, using AnnotationConfigApplicationContext - everything works good. With SpringJUnit4ClassRunner - it does not. I guess I miss something in my test code, but I do not have enough knowledge to realize what.
Interface:
package bakery.intrface;
#FunctionalInterface
public interface Dessert {
void introduce();
}
Cake:
package bakery.desserts;
import bakery.intrface.Dessert;
import org.springframework.stereotype.Component;
#Component
public class Cake implements Dessert {
#Override
public void introduce() {
System.out.println("I am a cake!");
}
}
Cookie:
package bakery.desserts;
import bakery.intrface.Dessert;
import org.springframework.stereotype.Component;
#Component
public class Cookie implements Dessert {
#Override
public void introduce() {
System.out.println("I'm a cookie!");
}
}
Ice cream:
package bakery.desserts;
import bakery.intrface.Dessert;
import org.springframework.stereotype.Component;
#Component
public class IceCream implements Dessert {
#Override
public void introduce() {
System.out.println("I'm an ice cream!");
}
}
The class, consumes some bean, Taster:
package bakery;
import bakery.intrface.Dessert;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;
#Component
public class Taster {
private Dessert dessert;
public void taste(){
dessert.introduce();
}
#Autowired
#Qualifier("iceCream")
public void setDessert(Dessert dessert) {
this.dessert = dessert;
}
}
Configuration:
package bakery.config;
import bakery.Bakery;
import bakery.Taster;
import bakery.desserts.Cake;
import bakery.intrface.Dessert;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
#ComponentScan(basePackageClasses = Bakery.class)
public class BakeryConfig {
}
Run class:
package bakery;
import bakery.config.BakeryConfig;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Bakery {
public static void main(String[] args) {
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(BakeryConfig.class);
String[] beans = context.getBeanDefinitionNames();
Taster taster = (Taster) context.getBean("taster");
taster.taste();
}
}
Test class:
package bakery;
import bakery.config.BakeryConfig;
import bakery.intrface.Dessert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import static org.junit.Assert.assertNotNull;
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration(classes = BakeryConfig.class)
public class BakeryTest {
#Autowired
Dessert dessert;
#Autowired
Taster taster;
#Test
public void contextInit(){
assertNotNull(dessert);
dessert.introduce();
}
#Test
public void tasterInit(){
assertNotNull(taster);
}
}
When I run the test, I'm getting the exception: No qualifying bean of type [bakery.intrface.Dessert] is defined: expected single matching bean but found 3: cookie,iceCream,cake.
There are 3 "Dessert" beans in your application context, you have to specify which one you want to wire.
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration(classes = BakeryConfig.class)
public class BakeryTest {
#Autowired
#Qualifier("iceCream") // <===================== you must specify which bean to be wired
Dessert dessert;
#Autowired
Taster taster;
This is to be expected.
The declaration
#Autowired
Dessert dessert;
is asking for a Dessert object. Dessert is the interface, and there are three implementing classes, Cookie, IceCream, and Cake. Since you haven't made it more explicit which of those implementations you want, Spring throws an error because it can't decide what to do.
If you need this in your test, you can do one of the following:
#Autowired
#Qualifier("iceCream")
Dessert dessert;
to get only the ice cream dessert,
OR
#Autowired
List<Dessert> desserts;
to get a list containing all the implementations.