Bring is a dependency injection framework. It uses IoC (Inversion of Control) container, which is represented by ApplicationContext, where beans are managed. The framework can create beans for you and inject them as dependencies to other beans
To install Bring locally you should:
- clone repo
https://github.com/hoverla-bobocode/Bring.git - go to the root of Bring project
cd <path_to_bring>/Bring - build jar with
mvn clean install -DskipTests - add jar to your maven project
<dependency>
<groupId>com.bobocode.hoverla</groupId>
<artifactId>bring</artifactId>
<version>1.0-SNAPSHOT</version>
</dependency>
Sorry for inconvenience, we're planning to move to maven central soon.
To easily start an application with Bring, use the BringApplication.loadContext("package.to.scan") method
import com.bobocode.hoverla.bring.BringApplication;
import com.bobocode.hoverla.bring.context.ApplicationContext;
public class DemoApp {
public static void main(String[] args) {
ApplicationContext applicationContext = BringApplication.loadContext("packages.to.scan"); // provide packages to be scanned for beans
}
}If you need to customize loading of ApplicationContext, you can do it with ApplicationContextBuilder. Here's an
example of its usage:
import ch.qos.logback.classic.Level;
import com.bobocode.hoverla.bring.BringApplication;
import com.bobocode.hoverla.bring.context.ApplicationContext;
public class DemoApp {
public static void main(String[] args) {
ApplicationContext applicationContext = BringApplication.getContextBuilder()
.logLevel(Level.DEBUG) // provide logging level
.packagesToScan("packages.to.scan") // provide packages to be scanned for beans
.build();
}
}Bean is a class that is managed by IoC container. To define a bean you have multiple options:
To define a bean with annotation configuration just annotate your desired bean class with @Bean annotation. Look at the next example:
import com.bobocode.hoverla.bring.annotation.Bean;
@Bean
public class MySimpleBean {
}By default, Bring generates a bean name as a fully qualified class name. You can customize it by providing a value
property for
the @Bean annotation
import com.bobocode.hoverla.bring.annotation.Bean;
@Bean("customBean")
public class MyCustomBean {
}If you have multiple beans of the same type, you can make the one preferable for injection without specifying the bean
name over the other ones by providing a primary value for
the @Bean annotation
import com.bobocode.hoverla.bring.annotation.Bean;
@Bean(primary = true)
public class MyPrimaryBean {
}If your class has dependencies that should be injected, you may use one of these types of injection:
A bean class has the following constraints:
- if a class has multiple constructors, mark the one with the fields that should be injected by Bring with @Inject annotation. If a class has only one constructor, the annotation is not necessary
- use only constructor injection or field injection. Using of both injection types is not recommended, because it may lead to unpredictable results
With Java Configuration you can provide a way how a bean should be instantiated via Java code. Use a @Configuration annotation to mark a class that will contain bean declarations. To declare a bean create a method and mark it as @Bean
import com.bobocode.hoverla.bring.annotation.Bean;
import com.bobocode.hoverla.bring.annotation.Configuration;
@Configuration
public class MyJavaConfiguration {
@Bean
public MyBean myBean() {
return new MyBean();
}
}By default, Bring will use a method name as a bean name. The bean name can be provided via the @Bean annotation by specifying its value
import com.bobocode.hoverla.bring.annotation.Bean;
import com.bobocode.hoverla.bring.annotation.Configuration;
@Configuration
public class MyJavaConfiguration {
@Bean("customBeanFromJavaConfiguration")
public MyCustomBean myCustomBean() {
return new MyCustomBean();
}
}It's also acceptable to mark a bean as primary for avoiding conflicts when there are multiple beans of the same type.
In that case bean marked as primary will be injected
import com.bobocode.hoverla.bring.annotation.Bean;
import com.bobocode.hoverla.bring.annotation.Configuration;
@Configuration
public class MyJavaConfiguration {
@Bean(primary = true)
public MyCustomBean myPrimaryCustomBean() {
return new MyCustomBean();
}
}If you want other beans to be injected inside a method, provide them as parameters
import com.bobocode.hoverla.bring.annotation.Configuration;
@Configuration
public class MyJavaConfiguration {
@Bean
public MyBeanWithDependency myBeanWithDependency(MySimpleBean mySimpleBean) {
return new MyBeanWithDependency(mySimpleBean);
}
}To specify a bean name use a @Qualifier annotation
import com.bobocode.hoverla.bring.annotation.Configuration;
@Configuration
public class MyJavaConfiguration {
@Bean
public MyBeanWithCustomDependency myBeanWithCustomDependency(@Qualifier("customBean") MyCustomBean myCustomBean) {
return new MyBeanWithCustomDependency(myCustomBean);
}
}To use constructor injection, provide beans, that you want to be injected, as parameters to your bean's constructor. If the bean has multiple constructors, the annotation @Inject should be provided. If only one constructor is present, the annotation is not necessary
import com.bobocode.hoverla.bring.annotation.Bean;
import com.bobocode.hoverla.bring.annotation.Inject;
@Bean
public class MyBeanWithDependencies {
private final MyCustomBean myCustomBean;
@Inject
public MyBeanWithDependencies(MyCustomBean myCustomBean) {
this.myCustomBean = myCustomBean;
}
public MyBeanWithDependencies() {
}
}If you want to specify a bean name (if there are multiple beans of the same type, for example), use
a @Qualifier annotation. If there are multiple
bean of the same type, and you want the one of them to be injected without specifying a bean name, mark it as primary
import com.bobocode.hoverla.bring.annotation.Bean;
import com.bobocode.hoverla.bring.annotation.Configuration;
@Configuration
public class MyJavaConfiguration {
@Bean("customBeanFromJavaConfiguration")
public MyCustomBean myCustomBean() {
return new MyCustomBean();
}
@Bean(primary = true)
public MyCustomBean myPrimaryCustomBean() {
return new MyCustomBean();
}
}import com.bobocode.hoverla.bring.annotation.Bean;
import com.bobocode.hoverla.bring.annotation.Inject;
import com.bobocode.hoverla.bring.annotation.Qualifier;
@Bean
public class MyBeanWithCustomDependencies {
private final MyCustomBean myPrimaryCustomBean;
private final MyCustomBean myCustomBean;
public MyBeanWithCustomDependencies(MyCustomBean myPrimaryCustomBean, @Qualifier("customBeanFromJavaConfiguration") MyCustomBean myCustomBean) {
this.myPrimaryCustomBean = myPrimaryCustomBean;
this.myCustomBean = myCustomBean;
}
}Beans may be injected right in the field without a constructor. To do it mark a field with an @Inject annotation
Please notice: Don't mark a field as final because it won't be injected and context load will be aborted
import com.bobocode.hoverla.bring.annotation.Bean;
import com.bobocode.hoverla.bring.annotation.Inject;
@Bean
public class MyBeanWithInjectedField {
@Inject
private MyCustomBean myCustomBean;
}If you need to provide a custom bean name, use a @Qualifier annotation.
import com.bobocode.hoverla.bring.annotation.Bean;
import com.bobocode.hoverla.bring.annotation.Inject;
import com.bobocode.hoverla.bring.annotation.Qualifier;
@Bean
public class MyBeanWithCustomInjectedField {
@Inject
@Qualifier("customBean")
private MyCustomBean myCustomBean;
}