Spring中@Conditional注解用法详解

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Conditional {
    /**
     * All {@link Condition Conditions} that must {@linkplain Condition#matches match}
     * in order for the component to be registered.
     */
    Class<? extends Condition>[] value();
}

package com.spring.bean;
 
 
public class Book {
    private String bookName;
    private String bookType;
    private double price;
 
 
    public Book(String bookName, String bookType, double price) {
        this.bookName = bookName;
        this.bookType = bookType;
        this.price = price;
    }
 
 
    public String getBookName() {
        return bookName;
    }
 
 
    public void setBookName(String bookName) {
        this.bookName = bookName;
    }
 
 
    public String getBookType() {
        return bookType;
    }
 
 
    public void setBookType(String bookType) {
        this.bookType = bookType;
    }
 
 
    public double getPrice() {
        return price;
    }
 
 
    public void setPrice(double price) {
        this.price = price;
    }
 
 
    @Override
    public String toString() {
        return "Book{" +
                "bookName='" + bookName + '\'' +
                ", bookType='" + bookType + '\'' +
                ", price=" + price +
                '}';
    }
}

package com.spring.condition;
 
 
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;
 
 
public class CNCondition implements Condition {
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
        // user.language=CN 表示中文返回 true
        return conditionContext.getEnvironment().getProperty("user.language").contains("cn");
    }
}

package com.spring.condition;
 
 
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;
 
 
public class ZHCondition implements Condition {
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
        // user.language=ZH Java默认语言 表示中文返回 true
        return conditionContext.getEnvironment()
        .getProperty("user.language").contains("zh");
    }
}

package com.spring.config;
 
 
import com.spring.bean.Book;
import com.spring.condition.CNCondition;
import com.spring.condition.ZHCondition;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Conditional;
import org.springframework.context.annotation.Configuration;
 
 
@Configuration
@Conditional(ZHCondition.class)
 
 
public class TestConditionalConfig {
    @Bean
    @Conditional(ZHCondition.class)//中文
    public Book bookZH()    {
        return new Book("红楼梦","中国古典书籍",99.9);
    }
 
 
    @Bean
    @Conditional(CNCondition.class)//英文
    public Book bookCN()    {
        return new Book("哈姆雷特","外国经典名著",66.6);
    }
}

package com.spring.test;
 
 
import com.spring.bean.Book;
import com.spring.config.TestConditionalConfig;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 
 
import java.util.Map;
 
 
public class TestConditional {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext annotationContext = new AnnotationConfigApplicationContext(TestConditionalConfig.class);
        Map<String, Book> map = annotationContext.getBeansOfType(Book.class);
        System.out.println(map);
    }
}