SpringBoot教程(7) @ConditionalOnProperty 详细讲解和示例
@ConditionalOnProperty 详细讲解和示例一、@ConditionalOnProperty简介二、详细代码示例1. 配置文件中配置2. 指定prefix+name3. 只指定name 或者 value3. 指定了havingValue4. 配置项是false,havingValue = false"5. 配置项是false,不设置havingValue6. 缺少配置,但配置了ma
@ConditionalOnProperty 详细讲解和示例
一、@ConditionalOnProperty简介
在开发基于SpringBoot的项目时,经常看到下面的条件注解:
- ConditionalOnProperty
- ConditionalOnResource
- ConditionalOnBean
- ConditionalOnClass
- ConditionalOnMissingBean
- ConditionalOnMissingClass
其中@ConditionalOnProperty是最为常见的一种,尤其用在自动配置类中,下面看下它的源码:
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.TYPE, ElementType.METHOD })
@Documented
@Conditional(OnPropertyCondition.class)
public @interface ConditionalOnProperty {
//name的别名,和value不可同时使用
String[] value() default {};
/**配置项的前缀,例如完整的配置是config.person.enable=true
* 那 prefix=“config.person”
*/
String prefix() default "";
/**
配置项的属性,例如完整的配置是config.person.enable=true
在前面已经设置 prefix=“config.person”
那么 name=“enable”;
如果prefix没有设置,那么name可以是整个配置项,例如下面:
name=“config.person.enable”,效果和上面的一样
*/
String[] name() default {};
/**
* 会将配置文件中的值和havingValue的值对比,如果一样则加载Bean,例如:
*
* config.person.enable=true,havingValue=“true”,加载Bean
*
* config.person.enable=false,havingValue=“false”,加载Bean
*
* config.person.enable=ok,havingValue=“ok”,加载Bean
*
* config.person.enable=false,havingValue=“true”,不加载Bean
*
* config.person.enable=ok,havingValue=“no”,不加载Bean
*
* 当然havingValue也可以不设置,只要配置项的值不是false或“false”,都加载Bean,例如:
*
* config.person.enable=ok,不设置havingValue,加载Bean
*
* config.person.enable=false,不设置havingValue,不加载Bean
*/
String havingValue() default "";
/**
* 如果在配置文件中没有该配置项,是否加载Bean
*/
boolean matchIfMissing() default false;
}
二、详细代码示例
1. 配置文件中配置
config:
person:
enable: true
2. 指定prefix+name
指定prefix+name,配置项的值不是false或“false”,加载Bean
@Configuration
public class MyBeanConfig {
@Bean
@ConditionalOnProperty(prefix = "config.person", name = "enable")
public Person person1(){
return new Person("Bill Gates", 66);
}
}
3. 只指定name 或者 value
只指定name 或者 value,要写完整配置项路径,配置项的值不是false或“false”,加载Bean
@Configuration
public class MyBeanConfig {
@Bean
@ConditionalOnProperty(value = "config.person.enable")
public Person person1(){
return new Person("Bill Gates", 66);
}
}
4. 指定了havingValue
指定了havingValue,要把配置项的值与havingValue对比,一致则加载Bean
@Bean
@ConditionalOnProperty(prefix = "config.person", name = "enable", havingValue = "true")
public Person person1(){
return new Person("Bill Gates", 66);
}
-
config.person.enable=true,havingValue=“true”,加载Bean
-
config.person.enable=false,havingValue=“false”,加载Bean
-
config.person.enable=ok,havingValue=“ok”,加载Bean
-
config.person.enable=false,havingValue=“true”,不加载Bean
-
config.person.enable=ok,havingValue=“no”,不加载Bean
-
当然havingValue也可以不设置,只要配置项的值不是false或“false”,都加载Bean
-
config.person.enable=ok,不设置havingValue,加载Bean
-
config.person.enable=false,不设置havingValue,不加载Bean
@Configuration
public class MyBeanConfig {
@Bean
@ConditionalOnProperty(prefix = "config.person", name = "ifenable")
public Person person1(){
return new Person("Bill Gates", 66);
}
}
上面代码配置项是true,但不设置havingValue,加载Bean
5. 配置项是false,havingValue = false"
配置项是false,havingValue = false",两者相等,加载Bean
config:
person:
enable: false
@Bean
@ConditionalOnProperty(prefix = "config.person", name = "enable", havingValue = "false")
public Person person1(){
return new Person("Bill Gates", 66);
}
6. 配置项是false,不设置havingValue
配置项是false,不设置havingValue,不加载Bean
@Bean
@ConditionalOnProperty(prefix = "config.person", name = "enable")
public Person person1(){
return new Person("Bill Gates", 66);
}
7. 缺少配置,但配置了matchIfMissing = true
配置文件缺少配置,但配置了matchIfMissing = true,加载Bean,否则不加载。
@Configuration
public class MyBeanConfig {
@Bean
@ConditionalOnProperty(prefix = "config.person", name = "enable",
havingValue = "true", matchIfMissing = true)
public Person person1(){
return new Person("Bill Gates", 66);
}
}
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