Spring 自定义条件装配

Spring 自定义条件装配

定义、：Bean装配前的前置判断
举例：@Profile，@Conditional
实现：注解方式，编程方式

注解方式

创建一个计算合的service

package com.imooc.diveinspringboot.service;

import org.springframework.stereotype.Service;

@Service
public interface CalculateService {
    Integer sum(Integer... values);
}

创建两个条件实现类

java7 for循环实现

package com.imooc.diveinspringboot.service;

import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Service;

/*
 * @author:ty
 * @create:2019-04-23 21:35
 * */
@Profile("Java7")
@Service
public class Java7CalculateService implements CalculateService{
    @Override
    public Integer sum(Integer... values) {
        System.out.println("使用java7 for循环实现");
        int sum=0;
        for (int i=0;i<values.length;i++)
        {
            sum+=values[i];
        }
            return sum;
    }
}

Java 0 lamada实现

package com.imooc.diveinspringboot.service;

import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Service;

import java.util.stream.Stream;

/*
 * @author:ty
 * @create:2019-04-23 21:35
 * */
@Profile("Java8")
@Service
public class Java8CalculateService implements CalculateService{
    @Override
    public Integer sum(Integer... values) {
            int sum= Stream.of(values).reduce(0,Integer::sum);
            return sum;
    }
}

然后再bootstrap

package com.imooc.diveinspringboot.bootstrap;

import com.imooc.diveinspringboot.service.CalculateService;
import org.springframework.boot.WebApplicationType;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;

/*
 * @author:ty
 * @create:2019-04-23 21:40
 * */
@SpringBootApplication(scanBasePackages = "com.imooc.diveinspringboot.service")
public class CalculateServiceBootStrap {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = new SpringApplicationBuilder(CalculateServiceBootStrap.class)
                .web(WebApplicationType.NONE)
                .profiles("Java7")   重点**
                .run(args);
        CalculateService calculateService=context.getBean(CalculateService.class);
        System.out.println(calculateService.sum(1,2,3,4,5,6,7,8,9,10));
        context.close();
    }
}

使用@Conditional

先创建一个自定义的注解@ ConditionalOnSystemProperty

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE,ElementType.METHOD})
@Documented
@Conditional(OnSystemPropertyCondition.class)
public @interface ConditionalOnSystemProperty {
    /*
    * java 系统属性名称
    * @return
    * */
    String name();
    /*
    * java系统属性值
    * @return
    * */
    String value();
}

然后创建OnSystemPropertyCondition类，它继承于conditon类，在里面写一些约束条件。

@Component
public class OnSystemPropertyCondition implements Condition {
    @Override
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {

        //获取注解的原信息
         Map<String,Object> attributes = annotatedTypeMetadata.getAnnotationAttributes
                 (ConditionalOnSystemProperty.class.getName());

         String propertyName = String.valueOf(attributes.get("name"));

        String propertyValue = String.valueOf(attributes.get("value"));

        String javaPropertyValue = System.getProperty(propertyName);

        return propertyValue.equals(javaPropertyValue);
    }
}

其中值得注意的是AnnotatedTypeMetadata ，这里面有注解的原信息，很重要。
然后再进行，bootstrap的测试，省略。