spring boot 的conditioanal的解析

一：

package com.zcp.springstart2;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.context.ConfigurableApplicationContext;

@SpringBootApplication

public class App {

public static void main(String[] args) {

ConfigurableApplicationContext context = SpringApplication.run(App.class, args);

System.out.println(System.getProperty("file.encoding"));

System.out.println(context.getBeansOfType(EncodingConvert.class));

System.out.println(">>>>>>>>>>>>>start>>>>>>>>>>>>");

System.out.println(context.getBeansOfType(Runnable.class));

System.out.println(">>>>>>>>>>>>>end>>>>>>>>>>>>");

context.close();

}

}

接口：

package com.zcp.springstart2;

public interface EncodingConvert {

}

接口的實現(xiàn):

package com.zcp.springstart2;

public class UTF8EncodingConvert implements EncodingConvert {

}

package com.zcp.springstart2;

public class GBKEncodingConvert implements EncodingConvert {

}

package com.zcp.springstart2;

import org.springframework.context.annotation.Condition;

import org.springframework.context.annotation.ConditionContext;

import org.springframework.core.type.AnnotatedTypeMetadata;

public class GBKCondition implements Condition {

@Override

public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {

String encoding = System.getProperty("file.encoding");

if(null != encoding){

return "gbk".equals(encoding.toLowerCase());

}

return false;

}

}

package com.zcp.springstart2;

import org.springframework.context.annotation.Condition;

import org.springframework.context.annotation.ConditionContext;

import org.springframework.core.type.AnnotatedTypeMetadata;

public class UTF8Condition implements Condition {

@Override

public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {

String encoding  = System.getProperty("file.encoding");

if(null != encoding){

return "utf-8".equals(encoding.toLowerCase());

}

return false;

}

}

常用的conditional的使用:

package com.zcp.springstart2;

import org.springframework.boot.SpringBootConfiguration;

import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;

import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;

import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;

import org.springframework.context.annotation.Bean;

@SpringBootConfiguration

public class UserConfig {

@Bean

@ConditionalOnProperty(name="runnable.enabled",havingValue="true",matchIfMissing=true)

public Runnable createRunnable(){

return new Runnable() {

@Override

public void run() {

System.out.println("UserConfig中的Runnable");

}

};

}

@Bean

@ConditionalOnClass(name="com.zcp.springstart2.User")

public Runnable createRunnableOnClass(){

return new Runnable() {

@Override

public void run() {

System.out.println("UserConfig中的createRunnableOnBean");

}

};

}

@Bean

@ConditionalOnBean(name="user")

public Runnable createRunnableOnBean(){

return new Runnable() {

@Override

public void run() {

System.out.println("UserConfig中的createRunnableOnBean");

}

};

}

}