Scope描述的是Spring容器是如何新建Bean的實例的。session
Spring經常使用的Scope有如下幾種,經過**@Scope**註解來實現:post
爲了更好的理解,咱們經過具體的代碼示例來理解下Singleton與ProtoType的區別。測試
package scope;
import org.springframework.stereotype.Service;
@Service
public class DemoSingletonService {
}
複製代碼
由於Spring默認配置的Scope是Singleton,所以以上代碼等價於如下代碼:spa
package scope;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Service;
@Service
@Scope("singleton")
public class DemoSingletonService {
}
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package scope;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Service;
@Service
@Scope("prototype")
public class DemoPrototypeService {
}
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package scope;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@ComponentScan("scope")
public class ScopeConfig {
}
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新建一個Main類,在main()方法中,分別從Spring容器中獲取2次Bean,而後判斷Bean的實例是否相等:prototype
package scope;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Main {
public static void main(String[] args) {
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ScopeConfig.class);
DemoSingletonService s1 = context.getBean(DemoSingletonService.class);
DemoSingletonService s2 = context.getBean(DemoSingletonService.class);
DemoPrototypeService p1 = context.getBean(DemoPrototypeService.class);
DemoPrototypeService p2 = context.getBean(DemoPrototypeService.class);
System.out.println("s1 與 s2 是否相等:" + s1.equals(s2));
System.out.println("p1 與 p2 是否相等:" + p1.equals(p2));
context.close();
}
}
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運行結果以下:code
從運行結果也能夠看出,默認狀況下即Singleton類型的Bean,無論調用多少次,只會建立一個實例。
Singleton類型的Bean,@Scope註解的值必須是:singleton。
ProtoType類型的Bean,@Scope註解的值必須是:prototype。
即便是大小寫不一致也不行,如咱們將DemoPrototypeService類的代碼修改成:
package scope;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Service;
@Service
@Scope("PROTOTYPE")
public class DemoPrototypeService {
}
複製代碼
此時運行代碼,就會報錯:
源碼地址:github.com/zwwhnly/spr…,歡迎下載。
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