SpringBoot配置

Condition

Condition是在Spring4.0增加的条件判断功能，通过这个功能可以实现选择型的创建Bean操作。
导入依赖

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>

<!--d导入jedis坐标-->
        <dependency>
            <groupId>redis.clients</groupId>
            <artifactId>jedis</artifactId>
        </dependency>

创建Beancom.itheima.springbootcondition.SpringbootConditionApplication

package com.itheima.springbootcondition;

        import org.springframework.boot.SpringApplication;
        import org.springframework.boot.autoconfigure.SpringBootApplication;
        import org.springframework.context.ConfigurableApplicationContext;

@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);

        /*//获取Bean，redisTemplate
        Object redisTemplate = context.getBean("redisTemplate");
        System.out.println(redisTemplate);*/

        Object user = context.getBean("user2"); //User
        System.out.println(user);

    }
}

package com.itheima.springbootcondition.domin;

public class User {
}

com.itheima.springbootcondition.condition.ClassCondition

package com.itheima.springbootcondition.condition;

import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;

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) {
        /*//1、需求：导入Jedis坐标后创建Bean
        //思路：判断redis.clients.jedis.Jedis文件是否存在
        boolean flag = true;
        try {
            Class<?> cls = Class.forName("redis.clients.jedis.Jedis");
        } catch (ClassNotFoundException e) {
            flag = false;
        }*/

        //2、需求：导入通过注解属性值value指定坐标后创建Bean
        //获取注解属性值 value
        Map<String, 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("redis.clients.jedis.Jedis");
            }
        } catch (ClassNotFoundException e) {
            flag = false;
        }
        //加真假条件
        return flag;
    }
}

com.itheima.springbootcondition.condition.ConditionOnClass

package com.itheima.springbootcondition.condition;

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();

}

com.itheima.springbootcondition.config.UserConfig

package com.itheima.springbootcondition.config;

import com.itheima.springbootcondition.condition.ConditionOnClass;
import com.itheima.springbootcondition.domin.User;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class UserConfig {

    @Bean
//    @Conditional(ClassCondition.class)
    //自定义注解原理
    @ConditionOnClass("redis.clients.jedis.Jedis")
    public User user(){
        return new User();
    }

    @Bean
    @ConditionalOnProperty(name = "itcast",havingValue = "itheima")
    public User user2(){
        return new User();
    }
}

application.properties

itcast=itheima

SpringBoot切换内置web服务器

SpringBoot的web环境中默认使用tomcat作为内置服务器，其实SpringBoot提供了4种内置服务器供我们选择，可以会为你方便的进行切换。