I have a config class with #ConfigurationProperties as follows. I am able to populate systemConfigMap from application.yaml in the MyConfig class as seen below
#ConfigurationProperties(prefix = "my-config")
#ConstructorBinding
#AllArgsConstructor
public class MyConfig {
/**
* A Configuration Map of multiple Systems
*/
private Map<String, SystemConfig> systemConfigMap;
}
the main class as
#EnableConfigurationProperties(MyConfig.class)
public class SpringApp {
public static void main(String[] args) {
SpringApplication.run(SpringApp.class, args);
}
}
The problem is that the generated bean name is my-config-a.b.c.config.MyConfig, which I am not able to use in payload-expression on spring integration http inbound gateway, I guess since it has "-" in it.
How can I specify the bean name for the generated bean MyConfig?
EDIT : HTTP Gateway Config
<int:channel id="myConfigListChannel" />
<int-http:inbound-gateway request-channel="myConfigListChannel"
path="/data"
error-channel="errorChannel"
supported-methods="GET"
payload-expression="#my-config-a.b.c.config.MyConfig.getSystemConfigMap().values()"
/>
I want to load the systemConfigMap values when /data is requested to start processing the flow.
When you try to use a complex bean id like yours my-config-a.b.c.config.MyConfig in the SpEL expression, you need to wrap it into the literal. Otherwise it understands an id until the first . which is treat as method/property reference to evaluate on a possible bean evaluate before.
So, it tries to find a bean like my-config-a and then tries to get access to its b property, which is fully false in your case.
To fix your problem you need to do like this:
payload-expression="#'my-config-a.b.c.config.MyConfig'.systemConfigMap.values()"
Another trick would be like your MyConfig injection into some bean with really meaningful bean name and use that one from the expression as a delegate.
Please explain the following about NoSuchBeanDefinitionException exception in Spring:
What does it mean?
Under what conditions will it be thrown?
How can I prevent it?
This post is designed to be a comprehensive Q&A about occurrences of NoSuchBeanDefinitionException in applications using Spring.
The javadoc of NoSuchBeanDefinitionException explains
Exception thrown when a BeanFactory is asked for a bean instance for
which it cannot find a definition. This may point to a non-existing
bean, a non-unique bean, or a manually registered singleton instance
without an associated bean definition.
A BeanFactory is basically the abstraction representing Spring's Inversion of Control container. It exposes beans internally and externally, to your application. When it cannot find or retrieve these beans, it throws a NoSuchBeanDefinitionException.
Below are simple reasons why a BeanFactory (or related classes) would not be able to find a bean and how you can make sure it does.
The bean doesn't exist, it wasn't registered
In the example below
#Configuration
public class Example {
public static void main(String[] args) throws Exception {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(Example.class);
ctx.getBean(Foo.class);
}
}
class Foo {}
we haven't registered a bean definition for the type Foo either through a #Bean method, #Component scanning, an XML definition, or any other way. The BeanFactory managed by the AnnotationConfigApplicationContext therefore has no indication of where to get the bean requested by getBean(Foo.class). The snippet above throws
Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException:
No qualifying bean of type [com.example.Foo] is defined
Similarly, the exception could have been thrown while trying to satisfy an #Autowired dependency. For example,
#Configuration
#ComponentScan
public class Example {
public static void main(String[] args) throws Exception {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(Example.class);
}
}
#Component
class Foo { #Autowired Bar bar; }
class Bar { }
Here, a bean definition is registered for Foo through #ComponentScan. But Spring knows nothing of Bar. It therefore fails to find a corresponding bean while trying to autowire the bar field of the Foo bean instance. It throws (nested inside a UnsatisfiedDependencyException)
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException:
No qualifying bean of type [com.example.Bar] found for dependency [com.example.Bar]:
expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {#org.springframework.beans.factory.annotation.Autowired(required=true)}
There are multiple ways to register bean definitions.
#Bean method in a #Configuration class or <bean> in XML configuration
#Component (and its meta-annotations, eg. #Repository) through #ComponentScan or <context:component-scan ... /> in XML
Manually through GenericApplicationContext#registerBeanDefinition
Manually through BeanDefinitionRegistryPostProcessor
...and more.
Make sure the beans you expect are properly registered.
A common error is to register beans multiple times, ie. mixing the options above for the same type. For example, I might have
#Component
public class Foo {}
and an XML configuration with
<context:component-scan base-packages="com.example" />
<bean name="eg-different-name" class="com.example.Foo />
Such a configuration would register two beans of type Foo, one with name foo and another with name eg-different-name. Make sure you're not accidentally registering more beans than you wanted. Which leads us to...
If you're using both XML and annotation-based configurations, make sure you import one from the other. XML provides
<import resource=""/>
while Java provides the #ImportResource annotation.
Expected single matching bean, but found 2 (or more)
There are times when you need multiple beans for the same type (or interface). For example, your application may use two databases, a MySQL instance and an Oracle one. In such a case, you'd have two DataSource beans to manage connections to each one. For (simplified) example, the following
#Configuration
public class Example {
public static void main(String[] args) throws Exception {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(Example.class);
System.out.println(ctx.getBean(DataSource.class));
}
#Bean(name = "mysql")
public DataSource mysql() { return new MySQL(); }
#Bean(name = "oracle")
public DataSource oracle() { return new Oracle(); }
}
interface DataSource{}
class MySQL implements DataSource {}
class Oracle implements DataSource {}
throws
Exception in thread "main" org.springframework.beans.factory.NoUniqueBeanDefinitionException:
No qualifying bean of type [com.example.DataSource] is defined:
expected single matching bean but found 2: oracle,mysql
because both beans registered through #Bean methods satisfied the requirement of BeanFactory#getBean(Class), ie. they both implement DataSource. In this example, Spring has no mechanism to differentiate or prioritize between the two. But such mechanisms exists.
You could use #Primary (and its equivalent in XML) as described in the documentation and in this post. With this change
#Bean(name = "mysql")
#Primary
public DataSource mysql() { return new MySQL(); }
the previous snippet would not throw the exception and would instead return the mysql bean.
You can also use #Qualifier (and its equivalent in XML) to have more control over the bean selection process, as described in the documentation. While #Autowired is primarily used to autowire by type, #Qualifier lets you autowire by name. For example,
#Bean(name = "mysql")
#Qualifier(value = "main")
public DataSource mysql() { return new MySQL(); }
could now be injected as
#Qualifier("main") // or #Qualifier("mysql"), to use the bean name
private DataSource dataSource;
without issue. #Resource is also an option.
Using wrong bean name
Just as there are multiple ways to register beans, there are also multiple ways to name them.
#Bean has name
The name of this bean, or if plural, aliases for this bean. If left
unspecified the name of the bean is the name of the annotated method.
If specified, the method name is ignored.
<bean> has the id attribute to represent the unique identifier for a bean and name can be used to create one or more aliases illegal in an (XML) id.
#Component and its meta annotations have value
The value may indicate a suggestion for a logical component name, to
be turned into a Spring bean in case of an autodetected component.
If that's left unspecified, a bean name is automatically generated for the annotated type, typically the lower camel case version of the type name. For example MyClassName becomes myClassName as its bean name. Bean names are case sensitive. Also note that wrong names/capitalization typically occur in beans referred to by string like #DependsOn("my BeanName") or XML config files.
#Qualifier, as mentioned earlier, lets you add more aliases to a bean.
Make sure you use the right name when referring to a bean.
More advanced cases
Profiles
Bean definition profiles allow you to register beans conditionally. #Profile, specifically,
Indicates that a component is eligible for registration when one or
more specified profiles are active.
A profile is a named logical grouping that may be activated
programmatically via
ConfigurableEnvironment.setActiveProfiles(java.lang.String...) or
declaratively by setting the spring.profiles.active property as a JVM
system property, as an environment variable, or as a Servlet context
parameter in web.xml for web applications. Profiles may also be
activated declaratively in integration tests via the #ActiveProfiles
annotation.
Consider this examples where the spring.profiles.active property is not set.
#Configuration
#ComponentScan
public class Example {
public static void main(String[] args) throws Exception {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(Example.class);
System.out.println(Arrays.toString(ctx.getEnvironment().getActiveProfiles()));
System.out.println(ctx.getBean(Foo.class));
}
}
#Profile(value = "StackOverflow")
#Component
class Foo {
}
This will show no active profiles and throw a NoSuchBeanDefinitionException for a Foo bean. Since the StackOverflow profile wasn't active, the bean wasn't registered.
Instead, if I initialize the ApplicationContext while registering the appropriate profile
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
ctx.getEnvironment().setActiveProfiles("StackOverflow");
ctx.register(Example.class);
ctx.refresh();
the bean is registered and can be returned/injected.
AOP Proxies
Spring uses AOP proxies a lot to implement advanced behavior. Some examples include:
Transaction management with #Transactional
Caching with #Cacheable
Scheduling and asynchronous execution with #Async and #Scheduled
To achieve this, Spring has two options:
Use the JDK's Proxy class to create an instance of a dynamic class at runtime which only implements your bean's interfaces and delegates all method invocations to an actual bean instance.
Use CGLIB proxies to create an instance of a dynamic class at runtime which implements both interfaces and concrete types of your target bean and delegates all method invocations to an actual bean instance.
Take this example of JDK proxies (achieved through #EnableAsync's default proxyTargetClass of false)
#Configuration
#EnableAsync
public class Example {
public static void main(String[] args) throws Exception {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(Example.class);
System.out.println(ctx.getBean(HttpClientImpl.class).getClass());
}
}
interface HttpClient {
void doGetAsync();
}
#Component
class HttpClientImpl implements HttpClient {
#Async
public void doGetAsync() {
System.out.println(Thread.currentThread());
}
}
Here, Spring attempts to find a bean of type HttpClientImpl which we expect to find because the type is clearly annotated with #Component. However, instead, we get an exception
Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException:
No qualifying bean of type [com.example.HttpClientImpl] is defined
Spring wrapped the HttpClientImpl bean and exposed it through a Proxy object that only implements HttpClient. So you could retrieve it with
ctx.getBean(HttpClient.class) // returns a dynamic class: com.example.$Proxy33
// or
#Autowired private HttpClient httpClient;
It's always recommended to program to interfaces. When you can't, you can tell Spring to use CGLIB proxies. For example, with #EnableAsync, you can set proxyTargetClass to true. Similar annotations (EnableTransactionManagement, etc.) have similar attributes. XML will also have equivalent configuration options.
ApplicationContext Hierarchies - Spring MVC
Spring lets you build ApplicationContext instances with other ApplicationContext instances as parents, using ConfigurableApplicationContext#setParent(ApplicationContext). A child context will have access to beans in the parent context, but the opposite is not true. This post goes into detail about when this is useful, particularly in Spring MVC.
In a typical Spring MVC application, you define two contexts: one for the entire application (the root) and one specifically for the DispatcherServlet (routing, handler methods, controllers). You can get more details here:
Difference between applicationContext.xml and spring-servlet.xml in Spring Framework
It's also very well explained in the official documentation, here.
A common error in Spring MVC configurations is to declare the WebMVC configuration in the root context with #EnableWebMvc annotated #Configuration classes or <mvc:annotation-driven /> in XML, but the #Controller beans in the servlet context. Since the root context cannot reach into the servlet context to find any beans, no handlers are registered and all requests fail with 404s. You won't see a NoSuchBeanDefinitionException, but the effect is the same.
Make sure your beans are registered in the appropriate context, ie. where they can be found by the beans registered for WebMVC (HandlerMapping, HandlerAdapter, ViewResolver, ExceptionResolver, etc.). The best solution is to properly isolate beans. The DispatcherServlet is responsible for routing and handling requests so all related beans should go into its context. The ContextLoaderListener, which loads the root context, should initialize any beans the rest of your application needs: services, repositories, etc.
Arrays, collections, and maps
Beans of some known types are handled in special ways by Spring. For example, if you tried to inject an array of MovieCatalog into a field
#Autowired
private MovieCatalog[] movieCatalogs;
Spring will find all beans of type MovieCatalog, wrap them in an array, and inject that array. This is described in the Spring documentation discussing #Autowired. Similar behavior applies to Set, List, and Collection injection targets.
For a Map injection target, Spring will also behave this way if the key type is String. For example, if you have
#Autowired
private Map<String, MovieCatalog> movies;
Spring will find all beans of type MovieCatalog and add them as values to a Map, where the corresponding key will be their bean name.
As described previously, if no beans of the requested type are available, Spring will throw a NoSuchBeanDefinitionException. Sometimes, however, you just want to declare a bean of these collection types like
#Bean
public List<Foo> fooList() {
return Arrays.asList(new Foo());
}
and inject them
#Autowired
private List<Foo> foos;
In this example, Spring would fail with a NoSuchBeanDefinitionException because there are no Foo beans in your context. But you didn't want a Foo bean, you wanted a List<Foo> bean. Before Spring 4.3, you'd have to use #Resource
For beans that are themselves defined as a collection/map or array
type, #Resource is a fine solution, referring to the specific
collection or array bean by unique name. That said, as of 4.3,
collection/map and array types can be matched through Spring’s
#Autowired type matching algorithm as well, as long as the element
type information is preserved in #Bean return type signatures or
collection inheritance hierarchies. In this case, qualifier values can
be used to select among same-typed collections, as outlined in the
previous paragraph.
This works for constructor, setter, and field injection.
#Resource
private List<Foo> foos;
// or since 4.3
public Example(#Autowired List<Foo> foos) {}
However, it will fail for #Bean methods, ie.
#Bean
public Bar other(List<Foo> foos) {
new Bar(foos);
}
Here, Spring ignores any #Resource or #Autowired annotating the method, because it's a #Bean method, and therefore can't apply the behavior described in the documentation. However, you can use Spring Expression Language (SpEL) to refer to beans by their name. In the example above, you could use
#Bean
public Bar other(#Value("#{fooList}") List<Foo> foos) {
new Bar(foos);
}
to refer to the bean named fooList and inject that.
I'm getting:
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.mz.server.rest.braintree.webhooks.SubscriptionWebhook]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.mz.server.rest.braintree.webhooks.SubscriptionWebhook.<init>()
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:85)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1098)
... 22 more
Even though I have defined this constructor in my applicatioContext-restapi.xml file:
<bean id="subscriptionWebhook" class="com.mz.server.rest.braintree.webhooks.SubscriptionWebhook">
<constructor-arg ref="dslContext" />
</bean>
Any idea why?
#RestController
public class SubscriptionWebhook {
private final static Logger LOGGER = Logger.getLogger(SubscriptionWebhook.class.getName());
private AdminService adminService;
public SubscriptionWebhook(DSLContext ctx) {
this.adminService = new AdminService(ctx);
}
}
Since Spring 3(ish) you can configure your container by applying #Component annotations to classes. #Controller annotation is defined as follows:
#Target(value=TYPE)
#Retention(value=RUNTIME)
#Documented
#Component
public #interface Controller
Which means classes annotated by it are going to get picked up, too. And RestController is just Controller and ResponseBody put together.
Anyway as you admitted in the comments you have enabled component scanning, and the configuration in xml is not going to get picked up in this case.
What you could do is convert the xml configuration to annotation-based injection, like that:
#RestController
public class SubscriptionWebhook {
private final static Logger LOGGER = Logger.getLogger(SubscriptionWebhook.class.getName());
private AdminService adminService;
public SubscriptionWebhook(#Qualifier("dslContext") DSLContext ctx) {
this.adminService = new AdminService(ctx);
}
}
Qualifier annotation is going to look in the container for a bean with name/id dslContext and inject it in the constructor. Alternatively you can use the javax.inject Named annotation, or if this is the only bean with that type, Spring's #Autowired or JSR-330's #Inject.
Annotation #RestController is autodetected by spring. Spring will create a bean for you so you shouldn't add bean definition in the xml, because it would create a second bean. If you want to inject another bean into the controller just use #Autowired. So the solution in your case is:
Remove "subscriptionWebhook" bean definition from the xml
Add #Autowired on SubscriptionWebhook constructor
I am moving from XML to annotations.
I have the interface types House and My , and class types HouseImpl and MyImpl. Spring injects an MyImpl instance into and MouseImpl instance,
public class HouseImpl implements House
private My my;
public My getMy2() {
return my;
}
#Autowired
public void setMy2(My my) {
this.my = my;
}
So the property in HouseImpl is called my2.
In the Spring configuration file,
<context:annotation-config></context:annotation-config>
<bean
id="house"
class="....HouseImpl"
>
...
</bean>
<bean
id="my"
class="my.test.own.spring_book_annotations.MyImpl"
>
</bean>
<bean
id="my2"
class="my.test.own.spring_book_annotations.MyImpl2"
>
</bean>
If the configuation is in XML, so there is autowired="byName" in the house configuration, and no #Autowired annotation, then bean my2 is injected, because the property name is my2 (setMy2 is the method). But when we use annotations bean my is injected, because the name of the argument of setMy2 is my.
My question is why #Autowired on the setter function does not look at the property name.
When #Autowired is used on a setter and there are multiple matching types, the container will look at the parameter name to find the bean to inject. In your case, the parameter is My my, so the my bean will be injected. You can change the parameter to My my2, or use #Qualifier("my2") to inject the my2 bean.
If you want to use the field name, place #Autowired on the field itself to use field-injection.
Your code is like this
#Autowired
public void setMy2(My my) {
this.my = my;
}
When you write annotation #Autowired, it will take the bean with setXXX name....here XXX is My2.
Hence your bean with my2 id is injected.
In order to specify the bean with id as my user #Qualifier annotation.
#Autowired
#Qualifier("my")
public void setMy2(My my) {
this.my = my;
}
How does Spring #Autowire beans: byName or byType? If one is not possible, is a second trial done using another mode?
If annotated with #Autowired it will inject the bean with the matching type (An exception will be thrown if there are more than one of a type). To specify a name use the #Qualifier annotation.
Springs #Autowire wires by type. For wiring by name you can also use
#Resource(name = "id")
The default mode of the #Autowired is byType.
Autowired annotation on variable or setters method is equivalent to xml attribute autowire="byType"
XML attribute autowire is defaut as no
"no":
The traditional Spring default. No automagical wiring. Bean references
must be defined in the XML file via the <ref/> element (or "ref"
attribute). We recommend this in most cases as it makes documentation
more explicit.
These are no, byName, byType, constructor, and autodetect. The default mode is no i.e. by default autowiring is turned off in traditional XML based configuration.
Using #Autowired annotation-
1) #Autowired on properties:
When #Autowired is used on properties, it is equivalent to autowiring by byType in configuration file.
2) #Autowired on property setters:
When #Autowired is used on setters, it is also equivalent to autowiring by byType in configuration file.
3) #Autowired on constructors:
When #Autowired is used on bean’s constructor, it is also equivalent to autowiring by constructor in configuration file.
Use #Qualifier for conflict in dependency resolution
As we learned that if we are using autowiring in byType mode and dependencies are looked for property class types. If no such type is found, an error is thrown. But, what if there are two or more beans for same class type.
In this case spring will not be able to choose correct bean to inject into property, and you will need to help the container using qualifiers.
To resolve a specific bean using qualifier, we need to use #Qualifier annotation along with #Autowired annotation and pass the bean name in annotation parameter.
I just checked out the source code of the spring-beans-5.2.7.RELEASE.jar. It contains class DefaultListableBeanFactory with the method
#Nullable
protected String determineAutowireCandidate(Map<String, Object> candidates, DependencyDescriptor descriptor) {
Class<?> requiredType = descriptor.getDependencyType();
String primaryCandidate = determinePrimaryCandidate(candidates, requiredType);
if (primaryCandidate != null) {
return primaryCandidate;
}
String priorityCandidate = determineHighestPriorityCandidate(candidates, requiredType);
if (priorityCandidate != null) {
return priorityCandidate;
}
// Fallback
for (Map.Entry<String, Object> entry : candidates.entrySet()) {
String candidateName = entry.getKey();
Object beanInstance = entry.getValue();
if ((beanInstance != null && this.resolvableDependencies.containsValue(beanInstance)) ||
matchesBeanName(candidateName, descriptor.getDependencyName())) {
return candidateName;
}
}
return null;
}
As we can see it tries to autowire by type. If no success it tries to autowire by name in this line
matchesBeanName(candidateName, descriptor.getDependencyName()))