SpirngBoot中@Conditional的初步学习使用

冷不防 2022-09-11 09:21 120阅读 0赞

@Conditional注解的作用是按照一定的条件进行判断，满足条件的会把对象装配到容器bean中。

下边上代码：

下边先写两个编码类，分别是UTF-8和GBK，均实现接口EncodingConverter

/**
     * 编码转换接口
     */
    public interface EncodingConverter {
    }

/**
     * GBK编码类
     */
    public class GBKEncodingConverter implements EncodingConverter {
    }

/**
     * UTF-8编码类
     */
    public class UTF8EncodingConverter implements EncodingConverter {
    }

下面来写编码的条件类，实现org.springframework.context.annotation.Condition接口：

public class GBKCondition implements Condition {
        @Override
        public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
            String encoding = System.getProperty("file.encoding");
            if ("gbk".equals(encoding.toLowerCase())){
                return true;
            }
            return false;
        }
    }

public class UTF8Condition implements Condition {
        @Override
        public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
            String encoding = System.getProperty("file.encoding");
            if ("utf-8".equals(encoding.toLowerCase())){
                return true;
            }
            return false;
        }
    }

下面接着写按条件装配到bean容器中的配置类：

@SpringBootConfiguration
    public class EncodingConverterConfig {
        @Bean
        @Conditional(GBKCondition.class)
        public GBKEncodingConverter createGBKConverter(){
            return new GBKEncodingConverter();
        }
    
        @Bean
        @Conditional(UTF8Condition.class)
        public EncodingConverter createUTF8Converter(){
            return new UTF8EncodingConverter();
        }
    }

接着上测试代码（直接写在启动类里面）：

@SpringBootApplication
    public class DemoApplication {
    
    	public static void main(String[] args) {
    		ConfigurableApplicationContext context = SpringApplication.run(DemoApplication.class, args);
    		Map<String, EncodingConverter> beansOfType = context.getBeansOfType(EncodingConverter.class);
    		System.out.println(beansOfType);
    		context.close();
    	}
    
    }

测试结果1：（会把GBK类装配到容器中）

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5bCY5bCP5paw_size_20_color_FFFFFF_t_70_g_se_x_16][]

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5bCY5bCP5paw_size_20_color_FFFFFF_t_70_g_se_x_16 1][]

测试结果2：（会把UTF8类装配到容器中）

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5bCY5bCP5paw_size_20_color_FFFFFF_t_70_g_se_x_16 2][]

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5bCY5bCP5paw_size_20_color_FFFFFF_t_70_g_se_x_16 3][]

注：@Conditional也可按多条件装配，是需要同时满足多个条件，才会将指定对象装配到容器中

@Conditional({GBKCondition.class,UTF8Condition.class})

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