@DependsOn或depends-on配置的使用

• 解釋：

首先要了解depends-on或@DependsOn做用，是用來表示一個bean A的實例化依賴另外一個bean B的實例化， 可是A並不須要持有一個B的對象，若是須要的話就不用depends-on，直接用依賴注入就能夠了或者ref標籤。

• @DependsOn用法

1：直接或者間接標註在帶有@Component註解的類上面;

2：直接或者間接標註在帶有@Bean 註解的方法上面;

code 用於帶有@Component註解的類上面:

package lantao.Dependson;

import org.springframework.context.annotation.DependsOn;
import org.springframework.stereotype.Component;

@Component
@DependsOn("dependson02")
public class Dependson01 {

	Dependson01(){
		System.out.println("Dependson01 success");
	}
}
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package lantao.Dependson;

import org.springframework.stereotype.Component;

@Component("dependson02")
public class Dependson02 {

	Dependson02(){
		System.out.println(" dependson02 Success ");
	}
}
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test:

package lantao.Dependson;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {
	public static void main(String[] args) {
		ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-bean-scan-dependson.xml");
	}
}
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結果：

dependson02 Success 
Dependson01 success

Process finished with exit code 0
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code 用於帶有@Bean註解的方法上面(Dependson01,Dependson02類上去掉了全部註解，這裏就不上代碼了):

package lantao.Dependson;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.DependsOn;

@Configuration
public class TestDependsOnMethod {

	@Bean("dependson01")
	@DependsOn("dependson02")
	public Dependson01 test1 (){
		return new Dependson01();
	}

	@Bean("dependson02")
	public Dependson02 test2 (){
		return new Dependson02();
	}
}
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結果：

dependson02 Success 
Dependson01 success

Process finished with exit code 0複製代碼

• depends-on用法(用在xml上)

code：

<bean id="testOneBean" class="lantao.sepl.TestOneBean" depends-on="testTWoBean"/>

<bean id="testTWoBean" class="lantao.sepl.TestTwoBean"/>複製代碼