Spring框架注解式开发（IDEA）——关于Conditional注解的具体使用（超详细）

@Conditional介绍

它的作用是按照一定的条件进行判断，需要注入的Bean满足给定条件才可以注入到IOC容器中。

举个经典例子：操作系统中你是用window还是linux

如果是window系统就不能用linux，如果是linux就不能用windows

下面开始先做使用配置

1.1 创建domain类

package com.Bean;

public class Person {
    private String name;
    private int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Bean{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

1.2 创建配置类Config，定义Bean

package com.Config;

import com.Bean.Person;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Lazy;
import org.springframework.context.annotation.Scope;

public class MainConfig {


    @Bean("bill")
    public Person person1(){
        return new Person("Bill",60);
    }

    @Bean("Lin")
    public Person person2(){
        return new Person("Lin",48);
    }
}

1.3 创建测试类，运行

@Test
public void Test03(){
    AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(MainConfig.class);
    String[] beanNamesForType = annotationConfigApplicationContext.getBeanNamesForType(Person.class);
    ConfigurableEnvironment environment = annotationConfigApplicationContext.getEnvironment();
    String property = environment.getProperty("os.name");
    System.out.println(property);
    for (String name:beanNamesForType) {
        System.out.println(name);
    }

}

 运行后我们发现IOC容器中管理了三个Bean，且操作系统现在为windows 10，下面我们来使用Conditional注解操作

二 Conditional注解使用详情

2.1创建二个类，windows，linux

package com.Conditional;

import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.context.annotation.Conditional;
import org.springframework.core.env.Environment;
import org.springframework.core.type.AnnotatedTypeMetadata;

public class Linux implements Condition {
    //ConditionContext：判断上下文环境
    //AnnotatedTypeMetadata,注释信息
    @Override
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
        //获取IOC使用beanfactory
        ConfigurableListableBeanFactory beanFactory = conditionContext.getBeanFactory();
        //获取当前环境信息
        Environment environment = conditionContext.getEnvironment();
        String property = environment.getProperty("os.name");
        //如果是linux系统返回真
        if(property.contains("linux")){
            return true;
        }
        return false;
    }
}

package com.Conditional;

import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.env.Environment;
import org.springframework.core.type.AnnotatedTypeMetadata;

public class windows implements Condition {
    //ConditionContext：判断上下文环境
    //AnnotatedTypeMetadata,注释信息
    @Override
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
        //获取当前环境信息
        Environment environment = conditionContext.getEnvironment();
        String property = environment.getProperty("os.name");
        //如果是Windows系统返回真
        if(property.contains("Windows")){
            return true;
        }
        return false;
    }
}

2.2 在Config中添加Conditional注解

@Conditional({windows.class})
@Bean("bill")
public Person person1(){
    return new Person("Bill",60);
}

@Conditional({Linux.class})
@Bean("Lin")
public Person person2(){
    return new Person("Lin",48);
}

2.3运行后

 最终我们得到了答案，因为Lin是在Linux操作系统下才会运行的，但是我们计算机是windows系统所以不会运行，则不会加载到IOC容器中

三 Conditional注解可以配置在方法上，也可以配置在类上

注意：如果我们配置到类上就必须满足这个操作条件才会让类方法的Bean加载到IOC容器中

3.1在类上添加注解Conditional 并设置为Linux系统

package com.Config;

import com.Bean.Person;
import com.Conditional.Linux;
import com.Conditional.windows;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Conditional;
import org.springframework.context.annotation.Lazy;
import org.springframework.context.annotation.Scope;

@Conditional({Linux.class})
public class MainConfig {

   @Conditional({windows.class})
    @Bean("bill")
    public Person person1(){
        return new Person("Bill",60);
    }

    @Conditional({Linux.class})
    @Bean("Lin")
    public Person person2(){
        return new Person("Lin",48);
    }
}

3.2运行

因为我们操作系统是Windows 10，如果不是Liunx系统，下面的方法全部都不会加载到IOC容器中，所以为空