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目录Conditional如何使用定义一个自定义标签自定义Conditionalconfig配置配置文件:application.propetiesSpringBootConditi
@Conditional 是 SpringFramework 的功能, SpringBoot 在它的基础上定义了 @ConditionalOnClass , @ConditionalOnProperty 的一系列的注解来实现更丰富的内容。
import com.example.conditional.MyConditional;
import org.springframework.context.annotation.Conditional;
import java.lang.annotation.*;
@Target({ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(MyConditional.class)
public @interface MyConditionalIAnnotation {
String key();
String value();
}
import com.example.conditional.interfaceI.MyConditionalIAnnotation;
import org.springframework.boot.autoconfigure.condition.ConditionOutcome;
import org.springframework.boot.autoconfigure.condition.SpringBootCondition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.context.annotation.Conditional;
import org.springframework.core.type.AnnotatedTypeMetadata;
import java.util.Map;
public class MyConditional extends SpringBootCondition {
@Override
public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
Map<String, Object> annotationAttributes = metadata.getAnnotationAttributes(MyConditionalIAnnotation.class.getName());
Object key = annotationAttributes.get("key");//
Object value = annotationAttributes.get("value");
if(key == null || value == null){
return new ConditionOutcome(false, "error");
}
//获取environment中的值
String key1 = context.getEnvironment().getProperty(key.toString());
if (value.equals(key1)) {
//如果environment中的值与指定的value一致,则返回true
return new ConditionOutcome(true, "ok");
}
return new ConditionOutcome(false, "error");
}
}
import com.example.conditional.interfaceI.MyConditionalIAnnotation;
import com.example.conditional.service.MyConditionalService;
import org.apache.log4j.Logger;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
public class MyConditionalConfig {
public static Logger logger=Logger.getLogger(MyConditionalService.class);
@MyConditionalIAnnotation(key = "com.example.conditional", value = "lbl")
@ConditionalOnClass(MyConditionalService.class)
@Bean
public MyConditionalService initMyConditionService() {
logger.info("MyConditionalService已加载。");
return new MyConditionalService();
}
}
spring.application.name=gateway
server.port=8084
#conditional 动态配置,判断该值是否等于lbl,是则创建MyConditionalService实例
com.example.conditional=lbl
#支持自定义aop
spring.aop.auto=true
Spring提供了多种实现化条件化配置的选择,如ConditionalOnProperty和ConditionalOnClass等。
用法如下:
@ConditionalOnProperty(prefix = "pkslow", name = "service", havingValue = "larry")
还有:
@ConditionalOnBean(仅仅在当前上下文中存在某个对象时,才会实例化一个Bean)
@ConditionalOnClass(某个class位于类路径上,才会实例化一个Bean)
@ConditionalOnExpression(当表达式为true的时候,才会实例化一个Bean)
@ConditionalOnMissingBean(仅仅在当前上下文中不存在某个对象时,才会实例化一个Bean)
@ConditionalOnMissinGClass(某个class类路径上不存在的时候,才会实例化一个Bean)
@ConditionalOnNotWEBApplication(不是web应用)
但有时候我们需要更灵活的自定义条件配置,这时可以通过继承SpringBootCondition类来实现。
自己根据需求实现自己的判断逻辑,我的实现如下:
public class PkslowCondition extends SpringBootCondition {
@Override
public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
BindResult<List<String>> maxBindResult = Binder.get(context.getEnvironment()).bind("pkslow.condition.max", Bindable.listOf(String.class));
BindResult<List<String>> minBindResult = Binder.get(context.getEnvironment()).bind("pkslow.condition.min", Bindable.listOf(String.class));
if ( (maxBindResult.isBound() && !maxBindResult.get().isEmpty()) && (minBindResult.isBound() && !minBindResult.get().isEmpty()) ) {
List<String> maxs = maxBindResult.get();
List<String> mins = minBindResult.get();
int max = Integer.parseInt(maxs.get(0));
int min = Integer.parseInt(mins.get(0));
if (max < 1000 && min > 0) {
return ConditionOutcome.match();
}
}
return ConditionOutcome.noMatch("pkslow.condition.max/pkslow.condition.min not matches");
}
}
表示需要有配置属性pkslow.condition.max/pkslow.condition.min才会生效,并且要求max<1000且min>0。
完成自定义的条件类后,就可以使用它来限定一个配置类是否要生效了,使用如下:
@Conditional(PkslowCondition.class)
@Configuration
public class PkslowConfig {
@PostConstruct
public void postConstruct() {
System.out.println("PkslowConfig called");
}
}
代码请查看:https://GitHub.com/LarryDpk/pkslow-samples
以上就是如何使用SpringBootCondition更自由地定义条件化配置的详细内容,更多关于SpringBootCondition 定义条件化配置的资料请关注编程网其它相关文章!
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