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spring bean autowire by type

Allows a property to be autowired if there is exactly one bean of the property type in the application context. If there is more than one, a fatal exception is thrown.

Let’s discuss spring bean autowire by type with below example. In below example we have SortNumbers class which have one dependency for sorting implementation. We use spring bean autowire by type here as we take sortAlgo as property name and in application context there is only one property exist of IsortAlgo type (BubbleSort).

Note: If there is more than one, a fatal exception is thrown or we have to provide the qualify information to help spring for identifying which one it should use.

We are using spring boot here.

Example

SpringAutowiringApplication.java

package com.codesjava.SpringAutowiring;
 
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
 
@SpringBootApplication
public class SpringAutowiringApplication {	
        private static ApplicationContext appContext;
 
	public static void main(String[] args) {
		appContext = SpringApplication.run(SpringAutowiringApplication.class, args);
		sort(new int[]{ 31,22,13,43,15,6,37});
	}
 
	private static void sort(int[] data) {
		SortNumbers sortNumers = (SortNumbers) appContext.getBean("sortNumbers");
		sortNumers.sortNumbers(data);		
	}
 
}

SortNumbers.java

package com.codesjava.SpringAutowiring;
 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
 
@Component
public class SortNumbers {
	@Autowired
	ISortAlgo sortalgo;	
 
	public void sortNumbers(int[] data){
		printNumbers(sortalgo.sort(data));
	}
 
	private static void printNumbers(int[] data) {          
        for (int i = 0; i < data.length; i++) {
            System.out.print(data[i]);
            if(i != data.length-1){
            	System.out.print(", ");
            }
        }
        System.out.println("\n");
    }    
}

ISortAlgo.java

package com.codesjava.SpringAutowiring;
 
public interface ISortAlgo {
	public int[] sort(int[] data);
}

BubbleSort.java

package com.codesjava.SpringAutowiring;
 
import org.springframework.stereotype.Component;
 
@Component
public class BubbleSort implements ISortAlgo {
	@Override
	public int[] sort(int[] array) {
		int n = array.length;
        int k;
        for (int m = n; m >= 0; m--) {
            for (int i = 0; i < n - 1; i++) {
                k = i + 1;
                if (array[i] > array[k]) {
                    swapNumbers(i, k, array);
                }
            }
        }
		return array;
	}	
 
	private void swapNumbers(int i, int j, int[] array) {  
        int temp;
        temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }
}

Output

6, 13, 15, 22, 31, 37, 43

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