摘要：本文通过讲解如何解析application.properties属性，介绍了几个注解的运用@Value @ConfigurationProperties @EnableConfigurationProperties @Autowired @ConditionalOnProperty
1 准备
1.1 搭建springboot
1.2 写一个controller类
package com.gbm.controller;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.ResponseBody;/** * Created by Administrator on 2019/2/20. */@Controllerpublic class IndexController { @RequestMapping("/index") @ResponseBody public String index() { return "我爱北京天安门！"; }}
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2 几种获取属性值方式
配置application.properties
value.local.province=Zhejiangvalue.local.city=Hangzhoucomplex.other.province=Jiangsucomplex.other.city=Suzhoucomplex.other.flag=false
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2.1 使用注解@Value("${xxx}")获取指定属性值
2.1.1 在controller类中获取属性值
package com.gbm.controller;import org.springframework.beans.factory.annotation.Value;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.ResponseBody;/** * Created by Administrator on 2019/2/20. */@Controllerpublic class IndexController { @Value("${value.local.province}") private String province; @Value("${value.local.city}") private String city; @RequestMapping("/index") @ResponseBody public String index() { StringBuffer sb = new StringBuffer(); sb.append(this.city); sb.append(","); sb.append(this.province); sb.append(" "); return sb.toString(); }}
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2.1.2 任何浏览器上运行 http://localhost:8080/index，结果如下
2.2 使用注解@ConfigurationProperties(prefix = "xxx")获得前缀相同的一组属性，并转换成bean对象
2.2.1 写一个实体类
package com.gbm.models;import org.springframework.boot.context.properties.ConfigurationProperties;import org.springframework.stereotype.Component;/** * Created by Administrator on 2019/2/21. */@Component@ConfigurationProperties(prefix = "complex.other")public class Complex { private String province; private String city; private Boolean flag; public String getProvince() { return province; } public void setProvince(String province) { this.province = province; } public String getCity() { return city; } public void setCity(String city) { this.city = city; } public Boolean getFlag() { return flag; } public void setFlag(Boolean flag) { this.flag = flag; } @Override public String toString() { return "Complex{" + "province=‘" + province + ‘\‘‘ + ", city=‘" + city + ‘\‘‘ + ", flag=" + flag + ‘}‘; }}
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2.2.2 在controller类中获取属性值
package com.gbm.controller;import com.gbm.models.Complex;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.ResponseBody;/** * Created by Administrator on 2019/2/20. */@Controllerpublic class IndexController { @Autowired private Complex complex; @RequestMapping("/index") @ResponseBody public String index() { return complex.toString(); }}
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2.2.3 在SpringBootApplication中使Configuration生效
package com.gbm.myspingboot;import com.gbm.models.Complex;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;import org.springframework.boot.context.properties.EnableConfigurationProperties;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.ComponentScans;@SpringBootApplication@ComponentScans({@ComponentScan("com.gbm.controller"), @ComponentScan("com.gbm.models")})@EnableConfigurationProperties(Complex.class)@ConditionalOnProperty(value = "complex.other.town", matchIfMissing = true)public class MyspingbootApplication { public static void main(String[] args) { SpringApplication.run(MyspingbootApplication.class, args); }}
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2.2.4 任何浏览器上运行 http://localhost:8080/index，结果如下
3 总结
关于解析application.properties文件，最重要的是对注解的使用，本文主要涉及到如下几个注解的运用
@Value("${xxx}")——获取指定属性值
@ConfigurationProperties(prefix = "xxx")——获得前缀相同的一组属性，并转换成bean对象
@EnableConfigurationProperties(xxx.class)——使Configuration生效，并从IOC容器中获取bean
@Autowired——自动注入set和get方法
@ConditionalOnProperty(value = "complex.other.town", matchIfMissing = true)——缺少该property时是否可以加载，如果是true，没有该property也会正常加载；如果是false则会抛出异常。例如
package com.gbm.myspingboot;import com.gbm.models.Complex;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;import org.springframework.boot.context.properties.EnableConfigurationProperties;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.ComponentScans;@SpringBootApplication@ComponentScans({@ComponentScan("com.gbm.controller"), @ComponentScan("com.gbm.models")})@EnableConfigurationProperties(Complex.class)@ConditionalOnProperty(value = "complex.other.town", matchIfMissing = false)public class MyspingbootApplication { public static void main(String[] args) { SpringApplication.run(MyspingbootApplication.class, args); }}
matchIfMissing=false代码
Error starting ApplicationContext. To display the conditions report re-run your application with ‘debug‘ enabled.2019-02-21 23:30:56.532 ERROR 3152 --- [ main] o.s.boot.SpringApplication : Application run failed
