01-SpringBoot高级-今日内容
- SpringBoot自定配置
- SpringBoot事件监听
- SpringBoot流程分析
- SpringBoot监控
- SpringBoot部署
02-SpringBoot自动配置-Condition-1
Condition是Spring4.0后引入的条件化配置接口，通过实现Condition接口可以完成有条件的加载相应的Bean
@Conditional要配和Condition的实现类（ClassCondition）进行使用
- ClassCondition
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
*/
@Override
public 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;
}
}
- UserConfig
@Configuration
public class UserConfig {
@Bean
@Conditional(ClassCondition.class)
public User user(){
return new User();
}
}
测试
@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);
}
}
03-SpringBoot自动配置-Condition-2
需求：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。
自定义条件注解类
import org.springframework.context.annotation.Conditional;
import java.lang.annotation.*;
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(ClassCondition.class)
public @interface ConditionOnClass {
String[] value();
}
**注意：**此处@ConditionOnClass为自定义注解
@Configuration
public class UserConfig {
@Bean
//@Conditional(ClassCondition.class)
@ConditionOnClass("com.alibaba.fastjson.JSON")
public User user(){
return new User();
}
@Bean
@ConditionalOnProperty(name = "itcast",havingValue = "itheima")
public User user2(){
return new User();
}
}
测试User对象的创建
@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);
}
}
动态获取
package com.itheima.springbootcondition.condtion;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.context.annotation.Conditional;
import org.springframework.core.type.AnnotatedTypeMetadata;
import java.lang.annotation.Annotation;
import java.util.Map;
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 注解的元对象，可以用于获取注解定义的属性值
* @return
*/
@Override
public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
导入Jedis坐标后创建bean
//boolean flag = true;
//try {
// Class<?> aClass = Class.forName("redis.clients.jedis.Jedis");
//} catch (ClassNotFoundException e) {
// e.printStackTrace();
// flag = false;
//}
//return flag;
// 导入指定坐标后创建bean
//获取注解属性值
Map<String, Object> annotationAttributes = metadata.getAnnotationAttributes(ConditionOnClass.class.getName());
//System.out.println(annotationAttributes);
String[] value = (String[])annotationAttributes.get("value");
boolean flag = true;
try {
for (String s : value) {
Class<?> aClass = Class.forName(s);
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
flag = false;
}
return flag;
}
}
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Bean
ConditionalOnClass：判断环境中是否有对应字节码文件才初始化Bean
ConditionalOnMissingBean：判断环境中没有对应Bean才初始化Bean
