yasin.bhojawala@gmail.com

Evaluation article on Different Types of Bean Injection in Spring

spring-core/src/main/java/com/baeldung/beaninjection/BeanConfiguration.java

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+package com.baeldung.beaninjection;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+import com.baeldung.beaninjection.domain.ConsoleLogger;
+import com.baeldung.beaninjection.domain.Logger;
+
+@Configuration
+@ComponentScan("com.baeldung.beaninjection")
+public class BeanConfiguration {
+
+    @Bean
+    public Logger logger() {
+        return new ConsoleLogger();
+    }
+
+    @Bean
+    public int maxChars() {
+        return 15;
+    }
+    
+    @Bean
+    public String messagePrefix(){
+        return "JConfig: ";
+    }
+}

spring-core/src/main/java/com/baeldung/beaninjection/MainApp.java

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+package com.baeldung.beaninjection;
+
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+
+import com.baeldung.beaninjection.domain.LoggingHelper;
+
+public class MainApp {
+    public static void main(String[] args) {
+
+        LoggingHelper logHelper = loadFromJavaConfig();
+        logHelper.logMessage("This is a log message");
+        
+        logHelper = loadFromXmlConfig();
+        logHelper.logMessage("This is another log message");
+    }
+
+    private static LoggingHelper loadFromJavaConfig() {
+        ApplicationContext context = new AnnotationConfigApplicationContext(BeanConfiguration.class);
+        
+        LoggingHelper loggingHelper = context.getBean(LoggingHelper.class);
+        ((ConfigurableApplicationContext)context).close();
+        
+        return loggingHelper;
+    }
+    
+    private static LoggingHelper loadFromXmlConfig() {
+        ApplicationContext context = new ClassPathXmlApplicationContext("beaninjection.xml");
+
+        LoggingHelper loggingHelper = context.getBean(LoggingHelper.class);
+        ((ConfigurableApplicationContext)context).close();
+        
+        return loggingHelper;
+    }
+}

spring-core/src/main/java/com/baeldung/beaninjection/domain/ConsoleLogger.java

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+package com.baeldung.beaninjection.domain;
+
+import org.springframework.beans.factory.annotation.Autowired;
+
+public class ConsoleLogger implements Logger {
+
+    private String messagePrefix;
+    private static final String DEFAULT_MESSAGE_PREFIX = "LOG: ";
+    
+    @Override
+    public void logMessage(String message, int maxChars) {
+        System.out.println(getMessagePrefix() + message.substring(0, maxChars));
+    }
+    
+    private String getMessagePrefix(){
+        return this.messagePrefix == null ? DEFAULT_MESSAGE_PREFIX : messagePrefix;
+    }
+
+    @Autowired
+    public void setMessagePrefix(String messagePrefix){
+        this.messagePrefix = messagePrefix;
+    }
+}

spring-core/src/main/java/com/baeldung/beaninjection/domain/Logger.java

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+package com.baeldung.beaninjection.domain;
+
+public interface Logger {
+
+    public void logMessage(String message, int maxChars);
+}

spring-core/src/main/java/com/baeldung/beaninjection/domain/LoggingHelper.java

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+package com.baeldung.beaninjection.domain;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class LoggingHelper {
+    private Logger logger;
+    private int maxChars;
+
+    @Autowired
+    public LoggingHelper(Logger logger, int maxChars) {
+        this.logger = logger;
+        this.maxChars = maxChars;
+    }
+
+    public void logMessage(String message) {
+        logger.logMessage(message, maxChars);
+    }
+}

spring-core/src/main/resources/beaninjection.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
+    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
+
+    <bean id="logHelper" class="com.baeldung.beaninjection.domain.LoggingHelper">
+        <constructor-arg index="0" ref="logger"/>
+        <constructor-arg index="1" type="int" value="20"/>
+    </bean>
+
+    <bean id="logger" class="com.baeldung.beaninjection.domain.ConsoleLogger">
+        <property name="messagePrefix" value="XMLConfig: "></property>
+    </bean>
+
+</beans>