Java EE 目录：https://blog.csdn.net/dkbnull/article/details/87932809
Spring Boot最常用的3种读取properties配置文件中数据的方法：
1、使用@Value注解读取
读取properties配置文件时，默认读取的是application.properties。
application.properties：
demo.name=Name
demo.age=18Java代码：
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class GatewayController {
@Value("${demo.name}")
private String name;
@Value("${demo.age}")
private String age;
@RequestMapping(value = "/gateway")
public String gateway() {
return "get properties value by ''@Value'' :" +
//1、使用@Value注解读取
" name=" + name +
" , age=" + age;
}
}运行结果如下：
这里，如果要把
@Value("${demo.name}")
private String name;
@Value("${demo.age}")
private String age;
部分放到一个单独的类A中进行读取，然后在类B中调用，则要把类A增加@Component注解，并在类B中使用@Autowired自动装配类A，代码如下。
类A：
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component
public class ConfigBeanValue {
@Value("${demo.name}")
public String name;
@Value("${demo.age}")
public String age;
}类B：
import cn.wbnull.springbootdemo.config.ConfigBeanValue;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class GatewayController {
@Autowired
private ConfigBeanValue configBeanValue;
@RequestMapping(value = "/gateway")
public String gateway() {
return "get properties value by ''@Value'' :" +
//1、使用@Value注解读取
" name=" + configBeanValue.name +
" , age=" + configBeanValue.age;
}
}
运行结果如下：
注意：如果@Value${}所包含的键名在application.properties配置文件中不存在的话，会抛出异常：
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'configBeanValue': Injection of autowired dependencies failed; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'demo.name' in value "${demo.name}"
2、使用Environment读取
application.properties：
demo.sex=男
demo.address=山东
Java代码：
import cn.wbnull.springbootdemo.config.ConfigBeanValue;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.env.Environment;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class GatewayController {
@Autowired
private ConfigBeanValue configBeanValue;
@Autowired
private Environment environment;
@RequestMapping(value = "/gateway")
public String gateway() {
return "get properties value by ''@Value'' :" +
//1、使用@Value注解读取
" name=" + configBeanValue.name +
" , age=" + configBeanValue.age +
"<p>get properties value by ''Environment'' :" +
//2、使用Environment读取
" , sex=" + environment.getProperty("demo.sex") +
" , address=" + environment.getProperty("demo.address");
}
}
运行，发现中文乱码：
这里，我们在application.properties做如下配置：
server.tomcat.uri-encoding=UTF-8
spring.http.encoding.charset=UTF-8
spring.http.encoding.enabled=true
spring.http.encoding.force=true
spring.messages.encoding=UTF-8
然后修改IntelliJ IDEA，File --> Settings --> Editor --> File Encodings ，将最下方Default encoding for properties files设置为UTF-8，并勾选Transparent native-to-ascii conversion。
重新运行结果如下：
3、使用@ConfigurationProperties注解读取
在实际项目中，当项目需要注入的变量值很多时，上述所述的两种方法工作量会变得比较大，这时候我们通常使用基于类型安全的配置方式，将properties属性和一个Bean关联在一起，即使用注解@ConfigurationProperties读取配置文件数据。
在src\main\resources下新建config.properties配置文件：
demo.phone=10086
demo.wife=self
创建ConfigBeanProp并注入config.properties中的值：
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;
@Component
@ConfigurationProperties(prefix = "demo")
@PropertySource(value = "config.properties")
public class ConfigBeanProp {
private String phone;
private String wife;
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public String getWife() {
return wife;
}
public void setWife(String wife) {
this.wife = wife;
}
}
@Component 表示将该类标识为Bean
@ConfigurationProperties(prefix = "demo")用于绑定属性，其中prefix表示所绑定的属性的前缀。
@PropertySource(value = "config.properties")表示配置文件路径。
使用时，先使用@Autowired自动装载ConfigBeanProp，然后再进行取值，示例如下：
import cn.wbnull.springbootdemo.config.ConfigBeanProp;
import cn.wbnull.springbootdemo.config.ConfigBeanValue;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.env.Environment;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class GatewayController {
@Autowired
private ConfigBeanValue configBeanValue;
@Autowired
private Environment environment;
@Autowired
private ConfigBeanProp configBeanProp;
@RequestMapping(value = "/gateway")
public String gateway() {
return "get properties value by ''@Value'' :" +
//1、使用@Value注解读取
" name=" + configBeanValue.name +
" , age=" + configBeanValue.age +
"<p>get properties value by ''Environment'' :" +
//2、使用Environment读取
" sex=" + environment.getProperty("demo.sex") +
" , address=" + environment.getProperty("demo.address") +
"<p>get properties value by ''@ConfigurationProperties'' :" +
//3、使用@ConfigurationProperties注解读取
" phone=" + configBeanProp.getPhone() +
" , wife=" + configBeanProp.getWife();
}
}
运行结果如下：
GitHub：https://github.com/dkbnull/SpringBootDemo
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