【Spring 基础】通过注解注入Bean

原课程：通过注解注入Bean

注入bean知识点思维导图

Spring 4.x推荐使用基于构造器的方式进行bean注入7.4.1 Dependency Injection
spring为什么推荐使用构造器注入

通过构造器和Set方法注入Bean

注意：通过构造器注入Bean时，如果只有一个构造器，可以不写@Autowired注解，详见17. Spring Beans and Dependency Injection


The following example shows a @Service Bean that uses constructor injection to obtain a required RiskAssessor bean:

package com.example.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class DatabaseAccountService implements AccountService {

	private final RiskAssessor riskAssessor;

	@Autowired
	public DatabaseAccountService(RiskAssessor riskAssessor) {
		this.riskAssessor = riskAssessor;
	}

	// ...

}

If a bean has one constructor, you can omit the @Autowired, as shown in the following example:

@Service
public class DatabaseAccountService implements AccountService {

	private final RiskAssessor riskAssessor;

	public DatabaseAccountService(RiskAssessor riskAssessor) {
		this.riskAssessor = riskAssessor;
	}

	// ...

}