（005）Spring Boot之读取配置文件

　　springboot的默认配置文件是application.properties或者application.yml。读取配置文件有以下两种方式

　　1、注入Environment对象，用Environment对象获取

　　2、使用Value注解

　　获取的值默认都是字符串类型，使用Value注解时，自动转化类型，使用Environment对象时，指定类，如下：

　　pom.xml

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.edu.spring</groupId>
    <artifactId>springboot</artifactId>
    <version>1.0.0</version>
    <packaging>jar</packaging>

    <name>springboot</name>
    <!-- FIXME change it to the project‘s website -->
    <url>http://www.example.com</url>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>2.1.6.RELEASE</version>
                <scope>import</scope>
                <type>pom</type>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

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

</project>

　　UserConfig.java

package com.edu.spring.springboot;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.env.Environment;
import org.springframework.stereotype.Component;

@Component
public class UserConfig {

    @Autowired
    private Environment environment;

    @Value("${local.port}")
    private String port;

    @Value("${local.port}")
    private Integer port2;

    public void show(){
        System.out.println("local.ip= "+environment.getProperty("local.ip"));
        System.out.println("local.port= "+environment.getProperty("local.port",Integer.class));
        System.out.println("local.port= "+port);
        System.out.println("local.port= "+port2);
    }
}

　　App.java

package com.edu.spring.springboot;

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(context.getEnvironment().getProperty("local.ip"));
        context.getBean(UserConfig.class).show();
        context.close();
    }
}

　　运行结果如下：

　　假如在配置文件中没对应的属性，取值的时候可以指定默认值，即配置文件中存在属性，取配置文件中的，否则取指定的。如下：

　　UserConfig.java

package com.edu.spring.springboot;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.env.Environment;
import org.springframework.stereotype.Component;

@Component
public class UserConfig {

    @Autowired
    private Environment environment;

    @Value("${name:你好}")
    private String name;

    public void show(){
        System.out.println("name= "+environment.getProperty("name","你好"));
        System.out.println("name= "+name);
    }
}

　　App.java

package com.edu.spring.springboot;

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);
        context.getBean(UserConfig.class).show();
        context.close();
    }
}

　　运行结果如下：

1

原文地址：https://www.cnblogs.com/javasl/p/11827832.html