（005）Spring Boot之读取配置文件

Posted 2020-11-29 明月之诗

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　　（一）配置文件中取值

　　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>

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　　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);
    }
}

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　　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();
    }
}

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　　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);
    }
}

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　　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();
    }
}

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　　运行结果如下：

　　springboot的默认配置文件可以放在classpath、classpath:/config、file、file:/config下面（file可以是任意名字），如下图所示：

　　（二）读取指定的配置文件

　　1、使用@PropertySource指定配置文件路径和名称，该注解可以多次使用，如下：

　　配置文件共4个

　　application.properties内容：url4=jdbc:mysql:localhost:3306/springboot4

　　jdbc.properties内容：url1=jdbc:mysql:localhost:3306/springboot1

　　jdbc2.properties内容：url2=jdbc:mysql:localhost:3306/springboot2

　　jdbc3.properties内容：url3=jdbc:mysql:localhost:3306/springboot3

　　FileConfig.java

package com.edu.spring.springboot;

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

@Configuration
@PropertySource("classpath:jdbc.properties")
@PropertySource("classpath:jdbc2/jdbc2.properties")
@PropertySource("file:/d:/1_1test/jdbc3.properties")
public class FileConfig {

}

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　　JdbcConfig.java

package com.edu.spring.springboot;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class JdbcConfig {

    @Value("${url1}")
    private String url1;
    
    @Value("${url2}")
    private String url2;
    
    @Value("${url3}")
    private String url3;
    
    @Value("${url4}")
    private String url4;
    
    public void show(){
        System.out.println("url1: "+url1);
        System.out.println("url2: "+url2);
        System.out.println("url3: "+url3);
        System.out.println("url4: "+url4);
    }
}

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　　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(JdbcConfig.class).show();
        context.close();
    }
}

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　　运行结果如下：

　　2、使用@PropertySources一次指定所有的配置文件

　　FileConfig.java

package com.edu.spring.springboot;

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.context.annotation.PropertySources;

@Configuration
@PropertySources({@PropertySource("classpath:jdbc.properties"),@PropertySource("classpath:jdbc2/jdbc2.properties"),
                  @PropertySource("file:/d:/1_1test/jdbc3.properties")})
public class FileConfig {

}

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　　运行结果如下：

　　（三）自动配置文件中的前缀

　　使用@ConfigurationProperties注解中的属性prefix或者value可以指定属性的前缀，结合属性的set方法可以取到配置文件中的属性值，如下：

　　application.properties

ds.url=jdbc:mysql:localhost:3306/springboot;
ds.driverClassName=com.mysql.jdbc.Driver;
ds.username=asdf;
ds.password=123456;

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　　DataSourceProperties.java

package com.edu.spring.springboot;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

@Component
@ConfigurationProperties(value="ds")
public class DataSourceProperties {

    private String url;
    
    private String driverClassName;
    
    private String username;
    
    private String password;

    public void setUrl(String url) {
        this.url = url;
    }

    public void setDriverClassName(String driverClassName) {
        this.driverClassName = driverClassName;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public void setPassword(String password) {
        this.password = password;
    }
    
    public void show(){
        System.out.println("--------------DataSourceProperties---------------");
        System.out.println("ds.url: "+url);
        System.out.println("ds.driverClassName: "+driverClassName);
        System.out.println("ds.username: "+username);
        System.out.println("ds.password: "+password);
    }
    
    
}

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　　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(DataSourceProperties.class).show();
        context.close();
    }
}

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　　运行结果如下：

　　（四）读取数组或者集合

　　application.properties

ds.hosts[0]=192.168.1.100
ds.hosts[1]=192.168.1.101
ds.hosts[2]=192.168.1.102

ds.sports[0]=8080
ds.sports[1]=8081
ds.sports[2]=8082
ds.sports[3]=8083

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　　TomcatProperties.java

package com.edu.spring.springboot;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

@Component
@ConfigurationProperties("ds")
public class TomcatProperties {

    private List<String> hosts=new ArrayList<String>();
    private String[] sports;

    public void setHosts(List<String> hosts) {
        this.hosts = hosts;
    }

    public void setSports(String[] sports) {
        this.sports = sports;
    }

    @Override
    public String toString() {
        return "TomcatProperties [hosts=" + hosts + ",sports="+Arrays.asList(sports)+"]";
    }

}

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　　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.getBean(TomcatProperties.class));
        context.close();
    }
}

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　　运行结果如下：

　　（四）启动时指定不同的配置文件

　　resources中有三个配置文件，如下图所示：

　　application.properties中内容：url=mysql:jdbc://127.0.0.1/db_springboot

　　application-test.properties中内容：url=mysql:jdbc://127.0.0.1/db_springboot_test

　　application-dev.properties中内容：url=mysql:jdbc://127.0.0.1/db_springboot_dev

　　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 )
    {
        SpringApplication app=new SpringApplication(App.class);
        app.setAdditionalProfiles("test");
        ConfigurableApplicationContext context=app.run(args);
        System.out.println(context.getEnvironment().getProperty("url"));
        context.close();
    }
}

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　　运行结果如下：

　　如果代码中的"test"修改为"dev"，则读取application-dev.properties中的url属性

　　如果注释掉代码中的app.setAdditionalProfiles行，则读取application.properties中的url属性

　　app.setAdditionalProfiles可以指定多个文件，如下：

　　添加配置文件application-aa.properties，内容是：name=hello application-aa.properties

　　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 )
    {
        SpringApplication app=new SpringApplication(App.class);
        app.setAdditionalProfiles("dev","test","aa");
        ConfigurableApplicationContext context=app.run(args);
        System.out.println(context.getEnvironment().getProperty("url"));
        System.out.println(context.getEnvironment().getProperty("name"));
        context.close();
    }
}

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　　运行结果如下：

　　备注：同时加载多个配置文件，且文件中有相同的属性时，则取后加载的，如同时加载了"dev"与"test"，则取"test"中的url。

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