add sample code for spring constructor di.

Author: peijd

spring-core/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    
+    <groupId>com.ripjava</groupId>
+    <artifactId>spring-core</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <dependencies>
+    
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-context</artifactId>
+            <version>5.1.9.RELEASE</version>
+        </dependency>
+
+    </dependencies>
+    
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.1</version>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

spring-core/src/main/java/com/ripjava/constructordi/Config.java

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+package com.ripjava.constructordi;
+
+import com.ripjava.constructordi.domain.Engine;
+import com.ripjava.constructordi.domain.Transmission;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("com.ripjava.constructordi")
+public class Config {
+
+    @Bean
+    public Engine engine() {
+        return new Engine("v8", 5);
+    }
+
+    @Bean
+    public Transmission transmission() {
+        return new Transmission("sliding");
+    }
+}

spring-core/src/main/java/com/ripjava/constructordi/SpringDIRunner.java

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+package com.ripjava.constructordi;
+
+import com.ripjava.constructordi.domain.Car;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+
+public class SpringDIRunner {
+    public static void main(String[] args) {
+        Car toyota = getCarFromXml();
+
+        System.out.println(toyota);
+
+        toyota = getCarFromJavaConfig();
+
+        System.out.println(toyota);
+    }
+
+    private static Car getCarFromJavaConfig() {
+        ApplicationContext context = new AnnotationConfigApplicationContext(Config.class);
+
+        return context.getBean(Car.class);
+    }
+
+    private static Car getCarFromXml() {
+        ApplicationContext context = new ClassPathXmlApplicationContext("constructordi.xml");
+
+        return context.getBean(Car.class);
+    }
+}

spring-core/src/main/java/com/ripjava/constructordi/domain/Car.java

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+package com.ripjava.constructordi.domain;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class Car {
+
+    private Engine engine;
+    private Transmission transmission;
+
+    @Autowired
+    public Car(Engine engine, Transmission transmission) {
+        this.engine = engine;
+        this.transmission = transmission;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("Engine: %s Transmission: %s", engine, transmission);
+    }
+}

spring-core/src/main/java/com/ripjava/constructordi/domain/Engine.java

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+package com.ripjava.constructordi.domain;
+
+public class Engine {
+    private String type;
+    private int volume;
+
+    public Engine(String type, int volume) {
+        this.type = type;
+        this.volume = volume;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("%s %d", type, volume);
+    }
+}

spring-core/src/main/java/com/ripjava/constructordi/domain/Transmission.java

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+package com.ripjava.constructordi.domain;
+
+
+public class Transmission {
+    private String type;
+
+    public Transmission(String type) {
+        this.type = type;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("%s", type);
+    }
+}

spring-core/src/main/resources/constructordi.xml

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+<beans xmlns="http://www.springframework.org/schema/beans"
+       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xsi:schemaLocation="http://www.springframework.org/schema/beans
+    https://www.springframework.org/schema/beans/spring-beans.xsd">
+    
+    <bean id="toyota" class="com.ripjava.constructordi.domain.Car">
+        <constructor-arg index="0" ref="engine" />
+        <constructor-arg index="1" ref="transmission" />
+    </bean>
+    
+    <bean id="engine"
+          class="com.ripjava.constructordi.domain.Engine">
+        <constructor-arg index="0" value="v4" />
+        <constructor-arg index="1" value="2" />
+    </bean>
+    
+    <bean id="transmission"
+          class="com.ripjava.constructordi.domain.Transmission">
+        <constructor-arg value="sliding" />
+    </bean>
+
+</beans>