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自定义条件#xff1a;
定义条件类#xff1a;自定义类实现Condition接口#xff0c;重写 matches 方法#xff0c;在 matches 方法中进行逻辑判断#xff0c;返回boolean值 。 matches 方法两个参数#xff1a; context#xff1a;上下文对象#xff0c;可…Condition
自定义条件
定义条件类自定义类实现Condition接口重写 matches 方法在 matches 方法中进行逻辑判断返回boolean值 。 matches 方法两个参数 context上下文对象可以获取属性值获取类加载器获取BeanFactory等。metadata元数据对象用于获取注解属性。 判断条件 在初始化Bean时使用 Conditional(条件类.class)注解
SpringBoot 提供的常用条件注解
ConditionalOnProperty判断配置文件中是否有对应属性和值才初始化BeanConditionalOnClass判断环境中是否有对应字节码文件才初始化BeanConditionalOnMissingBean判断环境中没有对应Bean才初始化Bean
示例1导入Jedis坐标后加载该Bean没导入则不加载
public class User {
}public class Role {
}Configuration
public class UserConfig {BeanConditional(ClassCondition.class)public User user(){return new User();}
}
public class ClassCondition implements Condition {/**** param context 上下文对象。用于获取环境IOC容器ClassLoader对象* param metadata 注解元对象。 可以用于获取注解定义的属性值* return*/Overridepublic boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {//1.需求 导入Jedis坐标后创建Bean//思路判断redis.clients.jedis.Jedis.class文件是否存在boolean flag true;try {Class? cls Class.forName(redis.clients.jedis.Jedis);} catch (ClassNotFoundException e) {flag false;}return flag;}SpringBootApplication
public class SpringbootConditionApplication {public static void main(String[] args) {//启动SpringBoot的应用返回Spring的IOC容器ConfigurableApplicationContext context SpringApplication.run(SpringbootConditionApplication.class, args);Object user context.getBean(user);System.out.println(user);}}示例2将类的判断定义为动态的。判断哪个字节码文件存在可以动态指定
Configuration
public class UserConfig {BeanConditionOnClass(redis.clients.jedis.Jedis)public User user(){return new User();}}
Target({ElementType.TYPE, ElementType.METHOD})
Retention(RetentionPolicy.RUNTIME)
Documented
Conditional(ClassCondition.class)
public interface ConditionOnClass {String[] value();
}
public class ClassCondition implements Condition {/**** param context 上下文对象。用于获取环境IOC容器ClassLoader对象* param metadata 注解元对象。 可以用于获取注解定义的属性值* return*/Overridepublic boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {//获取注解属性值 valueMapString, Object map metadata.getAnnotationAttributes(ConditionOnClass.class.getName());//System.out.println(map);String[] value (String[]) map.get(value);boolean flag true;try {for (String className : value) {Class? cls Class.forName(className);}} catch (ClassNotFoundException e) {flag false;}return flag;}
}示例3ConditionalOnProperty配置作用
Configuration
public class UserConfig {BeanConditionalOnProperty(name spring,havingValue zhangsan)public User user(){return new User();}}application.properties
springzhagnsanImport注解
Enable*底层依赖于Import注解导入一些类使用Import导入的类会被Spring加载到IOC容器中。而Import提供4中用法
导入Bean导入配置类导入 ImportSelector 实现类。一般用于加载配置文件中的类导入 ImportBeanDefinitionRegistrar 实现类。
示例0Enable
EnableUser
SpringBootApplication
public class SpringbootEnableApplication {public static void main(String[] args) {ConfigurableApplicationContext context SpringApplication.run(SpringbootEnableApplication.class, args);//获取BeanObject user context.getBean(user);System.out.println(user);}Target(ElementType.TYPE)
Retention(RetentionPolicy.RUNTIME)
Documented
Import(UserConfig.class)
public interface EnableUser {
}
public class UserConfig {Beanpublic User user() {return new User();}Beanpublic Role role() {return new Role();}
}
示例一导入Bean
Import(User.class)
SpringBootApplication
public class SpringbootEnableApplication {public static void main(String[] args) {ConfigurableApplicationContext context SpringApplication.run(SpringbootEnableApplication.class, args);User user context.getBean(User.class);System.out.println(user);
}示例二导入配置类
public class UserConfig {Beanpublic User user() {return new User();}Beanpublic Role role() {return new Role();}
}
Import(UserConfig.class)
SpringBootApplication
public class SpringbootEnableApplication {public static void main(String[] args) {ConfigurableApplicationContext context SpringApplication.run(SpringbootEnableApplication.class, args);User user context.getBean(User.class);System.out.println(user);Role role context.getBean(Role.class);System.out.println(role);
}示例3导入ImportSelector的实现类
public class MyImportSelector implements ImportSelector {Overridepublic String[] selectImports(AnnotationMetadata importingClassMetadata) {return new String[]{com.release.domain.User, com.release.domain.Role};}
}Import(MyImportSelector.class)
SpringBootApplication
public class SpringbootEnableApplication {public static void main(String[] args) {ConfigurableApplicationContext context SpringApplication.run(SpringbootEnableApplication.class, args);User user context.getBean(User.class);System.out.println(user);Role role context.getBean(Role.class);System.out.println(role);
}示例4导入 ImportBeanDefinitionRegistrar 实现类
public class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {Overridepublic void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {AbstractBeanDefinition beanDefinition BeanDefinitionBuilder.rootBeanDefinition(User.class).getBeanDefinition();registry.registerBeanDefinition(user, beanDefinition);}
}Import({MyImportBeanDefinitionRegistrar.class})
SpringBootApplication
public class SpringbootEnableApplication {public static void main(String[] args) {ConfigurableApplicationContext context SpringApplication.run(SpringbootEnableApplication.class, args);Object user context.getBean(user);System.out.println(user);MapString, User map context.getBeansOfType(User.class);System.out.println(map);
}EnableAutoConfiguration 注解 EnableAutoConfiguration 注解内部使用 Import(AutoConfigurationImportSelector.class)来加载配置类。 配置文件位置META-INF/spring.factories该配置文件中定义了大量的配置类当 SpringBoot 应用启动时会自动加载这些配置类初始化Bean 并不是所有的Bean都会被初始化在配置类中使用Condition来加载满足条件的Bean
示例自定义redis-starter。要求当导入redis坐标时SpringBoot自动创建Jedis的Bean。 实现步骤
1.创建 redis-spring-boot-autoconfigure 模块2.创建 redis-spring-boot-starter 模块,依赖 redis-spring-boot-autoconfigure的模块3.在 redis-spring-boot-autoconfigure 模块中初始化 Jedis 的 Bean。并定义META-INF/spring.factories 文件4.在测试模块中引入自定义的 redis-starter 依赖测试获取 Jedis 的Bean操作 redis。
3.在 redis-spring-boot-autoconfigure 模块中初始化 Jedis 的 Bean。并定义META-INF/spring.factories 文件
Configuration
EnableConfigurationProperties(RedisProperties.class)
ConditionalOnClass(Jedis.class)
public class RedisAutoConfiguration {/*** 提供Jedis的bean*/BeanConditionalOnMissingBean(name jedis)public Jedis jedis(RedisProperties redisProperties) {System.out.println(RedisAutoConfiguration....);return new Jedis(redisProperties.getHost(), redisProperties.getPort());}
}ConfigurationProperties(prefix redis)
public class RedisProperties {private String host localhost;private int port 6379;public String getHost() {return host;}public void setHost(String host) {this.host host;}public int getPort() {return port;}public void setPort(int port) {this.port port;}
}META-INF/spring.factories
org.springframework.boot.autoconfigure.EnableAutoConfiguration\com.release.redis.config.RedisAutoConfiguration4.在测试模块中引入自定义的 redis-starter 依赖测试获取 Jedis 的Bean操作 redis。
SpringBootApplication
public class SpringbootEnableApplication {public static void main(String[] args) {ConfigurableApplicationContext context SpringApplication.run(SpringbootEnableApplication.class, args);Jedis jedis context.getBean(Jedis.class);System.out.println(jedis);Beanpublic Jedis jedis(){return new Jedis(123.56.72.62,6379);}}
