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Spring-boot读取properties/yaml配置文件

在使用各种各样的框架开发的时候, 通常都需要处理一些配置文件, 无论是框架自带的还是我们自己定义的, 下面对Spring boot中读取配置文件的方法做一个总结.

配置文件可以有多种格式, 理论上只要你能从里面把需要的信息读取出来, 你想怎么存就怎么存, 不过还是有几种主流的配置方式.

下面对两种主要的配置文件格式: properties, yaml 进行总结.

Properties

现在要在项目中使用阿里的druid连接池, 把需要的参数都写入到properties配置文件中.

先建立一个项目, 项目结构如下:

.
├── build.gradle
├── settings.gradle
└── src
    ├── main
    │   ├── java
    │   │   └── top
    │   │       └── zenghao
    │   │           └── config
    │   │               ├── config
    │   │               │   └── DbConfig.java
    │   │               └── ConfigApplication.java
    │   └── resources
    │       ├── application.properties
    │       ├── db.properties
    │       ├── static
    │       └── templates
    └── test
        └── java
            └── top
                └── zenghao
                    └── config
                        └── ConfigApplicationTests.java

17 directories, 11 files

build.gradle

buildscript {
    ext {
        springBootVersion = '2.1.2.RELEASE'
    }
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
    }
}

apply plugin: 'java'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'

group = 'top.zenghao'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
}

测试代码: ConfigApplication.java

package top.zenghao.config;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import javax.sql.DataSource;
import javax.xml.crypto.Data;
import java.sql.*;

@RunWith(SpringRunner.class)
@SpringBootTest
public class ConfigApplicationTests {

    @Autowired
    private DataSource dataSource;

    @Test
    public void testDataSourceProperties() throws SQLException {
        String create_sql = "create table if not exists testproperties(" +
                "id int primary key," +
                "message varchar(50));";

        String drop_sql = "drop table testproperties";
        Connection connection = dataSource.getConnection();

        PreparedStatement statement = connection.prepareStatement(create_sql);

        statement.execute();

        PreparedStatement dropStatement = connection.prepareStatement(drop_sql);

        dropStatement.execute();
    }
}

方法一: 使用Environment手动读取

通过注入的Enviroment变量, 我们可以从中获取到application.properties中的参数, 使用这个方法必须把参数写到application.properties中.

application.properties

jdbc.url=jdbc:mysql://localhost:3306/testdb
jdbc.user=root
jdbc.password=pass
jdbc.driver=com.mysql.jdbc.Driver

DbConfig.java

package top.zenghao.config.config;

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.env.Environment;

import javax.sql.DataSource;

@Configuration
public class DbConfig {

    @Autowired
    private Environment env;	// 注入env

    @Bean
    @Primary
    public DataSource getDataSource() {
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setUsername(env.getProperty("jdbc.user"));
        dataSource.setPassword(env.getProperty("jdbc.password"));
        dataSource.setDriverClassName(env.getProperty("jdbc.driver"));
        dataSource.setUrl(env.getProperty("jdbc.url"));

        return dataSource;
    }
}

方法二: 使用 `@ConfigurationProperties` 注解自动读取

使用 @ConfigurationProperties 注解, Spring 会帮我们读取指定properties文件中的参数, 并且映射到相应的类字段中. 指明properties文件使用 @PropertySource

现在我们不把参数放到 application.properties 文件里面了, 而是新建一个配置文件 db.properties :

db.properties

jdbc.url=jdbc:mysql://localhost:3306/testdb
jdbc.user=root
jdbc.password=pass
jdbc.driver=com.mysql.jdbc.Driver

然后再新建一个Properties类

DbConfigProperties.java

package top.zenghao.config.config;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

@Configuration
@ConfigurationProperties(prefix = "jdbc")
@PropertySource("classpath:db.properties")
public class DbConfigProperties {
    private String url;
    private String driver;
    private String user;
    private String password;
	
    // getters and setters
}

在DbConfig.java中注册一个Bean:

DbConfig.java

package top.zenghao.config.config;

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.env.Environment;

import javax.sql.DataSource;

@Configuration
public class DbConfig {

    @Autowired
    private DbConfigProperties dbConfigProperties;

    /**
     * 方法二, 使用注解自动读取
     */
    @Bean
    @Primary
    public DataSource getDataSource2() {
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setUsername(dbConfigProperties.getUser());
        dataSource.setPassword(dbConfigProperties.getPassword());
        dataSource.setUrl(dbConfigProperties.getUrl());
        dataSource.setDriverClassName(dbConfigProperties.getDriver());

        return dataSource;
    }
}

嗯~看上去和第一种差不多, 不过这次我们能读取自定义的properties文件了.

方法三: 使用@Value注解

spring会对 @Value 注解的对象进行注入, 注入的内容是可以是 application.properties 中的配置属性, 也可以是别的, 具体需要看@Value的文档, 这里不展开讲. 注入的语法是SpEL, 例如下面这样:

DbConfig.java

@Bean
@Primary
*/
    public DataSource getDataSource3(@Value("${jdbc.user}") String user,
                                     @Value("${jdbc.password}") String password,
                                     @Value("${jdbc.driver}") String driver,
                                     @Value("${jdbc.url}") String url) {
    DruidDataSource dataSource = new DruidDataSource();
    dataSource.setUsername(user);
    dataSource.setPassword(password);
    dataSource.setDriverClassName(driver);
    dataSource.setUrl(url);

    return dataSource;
}

方法四: 使用Bundle

这个方法其实挺原始的, 不过它有用.

DbConfig.java

@Bean
@Primary
public DataSource getDataSource4() throws IOException {
    // Bundle 使用方法一

    /*
        ResourceBundle bundle
                = new PropertyResourceBundle(getClass().getClassLoader().getResourceAsStream("db.properties"));
        */

    // Bundle 方法二
    ResourceBundle bundle = ResourceBundle.getBundle("db");

    DruidDataSource dataSource = new DruidDataSource();
    dataSource.setUsername(bundle.getString("jdbc.user"));
    dataSource.setPassword(bundle.getString("jdbc.password"));
    dataSource.setUrl(bundle.getString("jdbc.url"));
    dataSource.setDriverClassName(bundle.getString("jdbc.driver"));

    return dataSource;
}