The recommended way is to use BeanFactory.getType for the specified bean name.
You can use either the binary name or the source name of the nested class, separated by a dollar sign ($) or a dot (.). For example, com.example.SomeThing$OtherThing or com.example.SomeThing.OtherThing.
The ClientService instance is created using the createInstance method, which returns a static instance of ClientService.
It shows that a POJO can have dependencies without relying on container-specific interfaces or annotations.
ThingOne demonstrates how multiple constructor arguments can be injected, highlighting the importance of type matching in dependency resolution.
It can be used to configure objects that have been created outside the control of an IoC container.
@ConstructorProperties
Constructor argument resolution matches by using the argument's type, and the order of arguments in the bean definition determines the order they are supplied during instantiation.
Constructor injection allows for the implementation of application components as immutable objects and ensures that required dependencies are not null, returning fully initialized components to the client code.
The 'id' attribute is a string that identifies the individual bean definition.
The ApplicationContext is initialized with configuration metadata, dependencies are expressed as properties or constructor arguments, and the Spring container validates the configuration as beans are created.
The <import/> element is used to load bean definitions from another file or files.
In Kotlin, the MovieFinder property is defined as a late-initialized property using 'lateinit var movieFinder: MovieFinder'.
A bean definition is essentially a recipe for creating one or more objects, containing configuration metadata that the container uses to instantiate the bean.
Beans should start with a lowercase letter and follow camel-case notation, such as accountManager or userDao.
Beans are typically defined using @Bean-annotated methods within a @Configuration class.
You can retrieve a bean instance using the method getBean(String name, Class<T> requiredType).
It specifies the constructor arguments for a bean, allowing Spring to inject dependencies.
Spring cannot determine the type of the value and cannot match by type without additional help.
The two major variants are Constructor-based dependency injection and Setter-based dependency injection.
Setter injection should primarily be used for optional dependencies that can have reasonable default values. It allows for reconfiguration or re-injection of dependencies later.
services.xml
The 'clientService' bean is created using the 'serviceLocator' factory bean and the 'createClientServiceInstance' factory method.
A BeanDefinition is used to configure the dependencies of beans in the Spring container.
The <alias/> element allows you to introduce an alias for a bean that is defined elsewhere, useful in large systems with split configurations.
Your application code should ideally avoid calls to the getBean() method and thus have no dependency on Spring APIs at all.
By the container calling setter methods on your beans after invoking a no-argument constructor or a no-argument static factory method.
Use constructors for mandatory dependencies and setter methods for optional dependencies. Constructor injection is preferred for required dependencies to ensure immutability and that dependencies are not null.
The class does not need to implement specific interfaces or be coded in a specific fashion; simply specifying the bean class should suffice. However, a default (empty) constructor may be needed depending on the IoC used.
Using relative paths creates a dependency on files outside the current application, which can lead to incorrect directory choices during runtime resolution.
The namespace provides the import directive feature, allowing for further configuration beyond plain bean definitions.
The ApplicationContext interface represents the Spring IoC container and is responsible for instantiating, configuring, and assembling the beans.
They are called collaborators or dependencies.
The <alias> tag allows a bean to be referred to by multiple names, creating a unique namespace for each reference while pointing to the same object.
A simple eight (or so) lines of boilerplate web descriptor XML in the web.xml file of the application typically suffices.
'Factory bean' refers to a general concept of a bean that creates objects, while 'FactoryBean' (capitalized) refers to a specific implementation class in Spring.
Beans are defined as <bean/> elements inside a top-level <beans/> element.
It defines the location of the XML schema for validation.
The Spring IoC container manages one or more beans, which are created based on the configuration metadata supplied to the container.
DAOs and business logic are usually responsible for creating and loading domain objects.
They state how the bean should behave in the container, including scope and lifecycle callbacks.
Bean definitions can span multiple XML files by using the application context constructor to load bean definitions from multiple Resource locations or by using the <import/> element to load definitions from other files.
They let the container load configuration metadata from various external resources, such as the local file system and the Java CLASSPATH.
The contents of the files being imported, including the top level <beans/> element, must be valid XML bean definitions.
The id and ref elements express the dependency between collaborating objects.
The Class property can be used to specify the bean class for direct construction or to specify the class containing a static factory method for bean creation.
In Spring 3.1, the id attribute was changed from an xsd:ID type to an xsd:string type, allowing more characters.
The two main packages are org.springframework.beans and org.springframework.context.
It is a POJO that has no dependencies on container specific interfaces, base classes, or annotations.
Your code must be compiled with the debug flag enabled.
The Groovy Bean Definition DSL is largely equivalent to XML bean definitions and supports Spring’s XML configuration namespaces.
The factory-bean attribute should specify the name of a bean that contains the instance method to be invoked.
The DefaultServiceLocator class is used to create instances of ClientService and AccountService, demonstrating how a factory bean can be managed and configured through dependency injection.
To ensure the container can properly reason about them during autowiring and other introspection steps.
Spring generates bean names by taking the simple class name and converting its initial character to lowercase.
You can load bean definitions from XML files in Java using the XmlBeanDefinitionReader, as shown in the example: new XmlBeanDefinitionReader(context).loadBeanDefinitions('services.xml', 'daos.xml');
ApplicationContext context = new GenericGroovyApplicationContext("services.groovy", "daos.groovy");
The index is 0-based.
DI makes code cleaner and enhances decoupling, allowing classes to be easier to test, especially when dependencies are on interfaces or abstract base classes.
A large number of constructor arguments is considered a bad code smell, indicating that the class may have too many responsibilities and should be refactored for better separation of concerns.
The 'class' attribute defines the type of the bean and uses the fully qualified classname.
In Java configuration, you can use the @Bean annotation to provide aliases for beans.
Unique.
If no name or id is supplied, the container generates a unique name for that bean.
IoC stands for Inversion of Control, which is a principle that is also known as Dependency Injection (DI). It involves the container injecting dependencies into objects rather than the objects controlling their own instantiation.
Because ThingTwo and ThingThree are not related by inheritance, allowing Spring to resolve the dependencies without needing explicit indexes or types.
A bean is an object that is instantiated, assembled, and managed by a Spring IoC container.
Constructor-based DI is accomplished by the container invoking a constructor with arguments that represent dependencies.
Configuration metadata represents how application developers instruct the Spring container to instantiate, configure, and assemble objects in their application.
It is common to create an instance of ClassPathXmlApplicationContext or FileSystemXmlApplicationContext.
daos.xml
The class attribute in the <bean/> element is usually mandatory, specifying the type of object to be instantiated.
Spring users typically configure beans using XML bean definitions, annotated components, or @Bean methods in Java-based @Configuration classes.
The GroovyBeanDefinitionReader is used to load bean definitions from Groovy files, similar to how XmlBeanDefinitionReader works for XML files.
ApplicationContext provides easier integration with AOP features, message resource handling for internationalization, event publication, and application-layer specific contexts.
The constructor allows the Spring container to inject a MovieFinder dependency.
Dependency Injection is a process where objects define their dependencies through constructor arguments, factory method arguments, or properties set after construction, and the container injects those dependencies when creating the bean.
The two fields are 'years' (an int) and 'ultimateAnswer' (a String).
The container gets its instructions on what objects to instantiate, configure, and assemble by reading configuration metadata.
Spring can convert values supplied in string format to built-in types like int, long, String, and boolean during the bean creation process.
The factory bean is used to create instances of other beans, such as 'clientService' and 'accountService', through specified factory methods.
The id attribute and the name attribute are used to specify bean identifiers.
Yes, a factory class can hold more than one factory method, as shown with 'createClientServiceInstance' and 'createAccountServiceInstance' in the example.
org.springframework.samples.jpetstore.dao.jpa.JpaAccountDao
The IoC container manages the instantiation and injection of dependencies for beans, allowing objects to define their dependencies through constructor arguments, factory method arguments, or properties.
You can use the 'index' attribute to explicitly specify the index of constructor arguments.
You can specify the constructor parameter name using the 'name' attribute for value disambiguation.
It is used for externalized configuration metadata, allowing bean definitions to be expressed in a Groovy file format.
The property name element refers to the name of the JavaBean property.
BeanDefinition objects represent bean definitions within the container and contain metadata such as the package-qualified class name of the bean.
The 'type' attribute allows the container to use type matching with simple types for constructor arguments.
Using fully qualified resource locations, such as 'file:C:/config/services.xml' or 'classpath:/config/services.xml', is preferable.
The factory-method attribute specifies the name of the method that will be invoked to create the bean instance.
Yes, Spring can manage non-bean-style classes, including legacy connection pools that do not adhere to the JavaBean specification.
It translates to a set of properties that make up each bean definition.
Configuration metadata is traditionally supplied in a simple and intuitive XML format.
The most flexible variant is GenericApplicationContext in combination with reader delegates.
Instantiation using an instance factory method invokes a non-static method of an existing bean, while static factory method instantiation calls a static method.
Configuration metadata can be represented in XML, Java annotations, or Java code.
The setter method allows the Spring container to inject a MovieFinder dependency into the SimpleMovieLister.
It supports registerSingleton(..) and registerBeanDefinition(..) methods.
org.springframework.samples.jpetstore.services.PetStoreServiceImpl
The 'DefaultServiceLocator' class contains methods to create instances of services, such as 'ClientService', and holds the service instances.
The ApplicationContext is an advanced factory interface that maintains a registry of different beans and their dependencies.
BeanFactory provides basic functionality and configuration framework, while ApplicationContext is a superset of BeanFactory that adds enterprise-specific features such as AOP integration, message resource handling, and event publication.
You can specify your bean class using the <bean> tag, for example: <bean id="exampleBean" class="examples.ExampleBean"/>.
Use the class attribute to specify the class containing the static factory method and an attribute named factory-method to specify the name of the factory method.
The Spring IoC container supports annotation-based configuration and Java-based configuration.
The annotations used include @Configuration, @Bean, @Import, and @DependsOn.
accountDao and itemDao
The GenericApplicationContext is used to create an application context that can load bean definitions from various sources, such as XML or Groovy files.
val service = context.getBean<PetStoreService>("petStore")
It provides a convenient mechanism for reading an InputStream from locations defined in a URI syntax.
It returns the DefaultListableBeanFactory implementation, allowing registration of existing objects created outside the container.
In Spring documentation, 'factory bean' refers to a bean that is configured in the Spring container and creates objects through an instance or static factory method.
The ApplicationContext supports both constructor-based and setter-based Dependency Injection.
Determining a bean's runtime type is non-trivial because the specified class in the bean metadata may not reflect the actual runtime type, especially if a factory method or a FactoryBean class is involved.
Typically, service layer objects, data access objects (DAOs), presentation objects, and infrastructure objects are defined as beans.
ApplicationContext context = new ClassPathXmlApplicationContext("services.xml", "daos.xml");
