package org.springframework.context.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Conditional {
    Class<? extends Condition>[] value();
}

@FunctionalInterface
public interface Condition {
    boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata);
}

public class MyCondition implements Condition {
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        Environment environment = context.getEnvironment();
        String isOpen = environment.getProperty("systemLog.isOpen");
        // 就算沒(méi)有設(shè)置systemLog.isOpen，那么isOpen就等于null，Boolean.valueOf對(duì)于null照樣會(huì)返回false的
        return Boolean.valueOf(isOpen);
    }
}

public class TestBean1 {
    @Override
    public String toString() {
        return super.toString() + "--我是TestBean1";
    }
}

@Configuration
@Conditional(MyCondition.class)
public class Myconfig {
    @Bean
    public TestBean1 testBean1(){
        return new TestBean1();
    }
}

@RestController
public class CommonController {
    @Autowired(required = false)
    private Myconfig myconfig;
	@Autowired(required = false)
    private TestBean1 testBean1;
    @RequestMapping("/import")
    public void printImportBeanInfo() {
        System.out.println(myconfig);
        System.out.println(testBean1);
    }
}

systemLog:
  isOpen: true

@Configuration
public class Myconfig {
    @Bean
    @Conditional(MyCondition.class)
    public TestBean1 testBean1(){
        return new TestBean1();
    }
}

public class ObstinateCondition implements Condition {
    @Override
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
         return false;
    }
}

@Configuration
@Conditional({MyCondition.class,ObstinateCondition.class})
public class Myconfig {
    @Bean
    public TestBean1 testBean1(){
        return new TestBean1();
    }
}

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional({OnClassCondition.class})
public @interface ConditionalOnClass {
	// 必須出現(xiàn)的類
    Class<?>[] value() default {};
	// 必須存在的類名，必須是全限類名，也就是包含包名+類名。
    String[] name() default {};
}

@Configuration
@ConditionalOnClass({TestBean2.class})
public class Myconfig {
    @Bean
    @ConditionalOnClass(name = "com.gzl.cn.springbootcache.config.TestBean3")
    public TestBean1 testBean1(){
        return new TestBean1();
    }
}

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional({OnClassCondition.class})
public @interface ConditionalOnMissingClass {
	// 必須不存在的類名稱，全類名
    String[] value() default {};
}

@ConditionalOnMissingClass("com.gzl.cn.springbootcache.config.TestBean5")

@ConditionalOnMissingClass(value = "com.gzl.cn.springbootcache.config.TestBean5")

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional({OnBeanCondition.class})
public @interface ConditionalOnBean {
	// 指定bean的類類型。當(dāng)所有指定類的bean都包含在容器中時(shí)，條件匹配。
    Class<?>[] value() default {};
	// 指定bean的全類名。當(dāng)指定的所有類的bean都包含在容器中時(shí)，條件匹配。
    String[] type() default {};
	// bean所聲明的注解,當(dāng)ApplicationContext中存在聲明該注解的bean時(shí)返回true
    Class<? extends Annotation>[] annotation() default {};
	// bean的id,當(dāng)ApplicationContext中存在給定id的bean時(shí)返回true,這個(gè)id指的就是容器當(dāng)中對(duì)象的id
    String[] name() default {};
	// 搜索容器層級(jí),默認(rèn)是所有上下文搜索
    SearchStrategy search() default SearchStrategy.ALL;
	// 可能在其泛型參數(shù)中包含指定bean類型的其他類
    Class<?>[] parameterizedContainer() default {};
}

@Configuration
public class Myconfig {
    @Bean
    public TestBean2 testBean2(){
        return new TestBean2();
    }
    @Bean
    @ConditionalOnBean(TestBean2.class)
    public TestBean1 testBean1() {
        return new TestBean1();
    }
}

@RestController
public class CommonController {
    @Autowired(required = false)
    private TestBean1 testBean1;
    @Autowired(required = false)
    private TestBean2 testBean2;
    @Autowired(required = false)
    private Myconfig myconfig;
    @RequestMapping("/import")
    public void printImportBeanInfo() {
        System.out.println(myconfig);
        System.out.println(testBean1);
        System.out.println(testBean2);
    }
}

@Bean
public TestBean2 testBean2(){
    return new TestBean2();
}

@Configuration
public class MyconfigTest {
    @Bean
    public TestBean2 testBean2(){
        return new TestBean2();
    }
}

@Order(Ordered.HIGHEST_PRECEDENCE) //最高優(yōu)先級(jí)

@Order(Ordered.LOWEST_PRECEDENCE) //最低優(yōu)先級(jí)

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.gzl.cn.springbootcache.config.MyconfigTest,\
com.gzl.cn.springbootcache.config.Myconfig

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional({OnBeanCondition.class})
public @interface ConditionalOnMissingBean {
    Class<?>[] value() default {};
    String[] type() default {};
	// 識(shí)別匹配 bean 時(shí)，可以被忽略的 bean 的 class 類型
    Class<?>[] ignored() default {};
	//識(shí)別匹配 bean 時(shí)，可以被忽略的 bean 的 class 類型名稱
    String[] ignoredType() default {};
    Class<? extends Annotation>[] annotation() default {};
    String[] name() default {};
    SearchStrategy search() default SearchStrategy.ALL;
    Class<?>[] parameterizedContainer() default {};
}

@Configuration
public class Myconfig {
    @Bean
    @ConditionalOnMissingBean(TestBean1.class)
    public TestBean1 testBean1() {
        return new TestBean1();
    }
}

@Configuration
public class Myconfig {
    @Bean
    @ConditionalOnMissingBean
    public TestBean1 testBean1() {
        System.out.println("1111111111");
        return new TestBean1();
    }
    @Bean
    @ConditionalOnMissingBean
    public TestBean1 testBean2() {
        System.out.println("2_222_222_222");
        return new TestBean1();
    }
}

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})
@Documented
@Conditional({OnPropertyCondition.class})
public @interface ConditionalOnProperty {
	// 指定的屬性完整名稱，不能和name同時(shí)使用。
    String[] value() default {};
	// //配置文件中屬性的前綴
    String prefix() default "";
	// //指定的屬性名稱
    String[] name() default {};
	// 指定的屬性的屬性值要等于該指定值，當(dāng)value或name為一個(gè)時(shí)使用
    String havingValue() default "";
	// 當(dāng)不匹配時(shí)是否允許加載，當(dāng)為true時(shí)就算不匹配也不影響bean的注入或配置類的生效。
    boolean matchIfMissing() default false;
}

@Configuration
@ConditionalOnProperty(
        prefix = "system.log",
        name = {"open"},
        havingValue = "true",
        matchIfMissing = false
)
public class Myconfig {
    @Bean
    public TestBean1 testBean1() {
        return new TestBean1();
    }
}

system:
  log:
    open: true