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Spring的@PropertySource注解使用

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@PropertySource注解是Spring用于加载配置文件,默认支持.properties.xml两种配置文件。@PropertySource属性如下:

接下来就使用@PropertySource来加载.properties.xml配置文件。这里模拟连接MySQL数据库。
首先添加依赖:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>5.1.6.RELEASE</version>
</dependency>

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-jdbc</artifactId>
    <version>5.1.6.RELEASE</version>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.26</version>
</dependency>
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.20</version>
</dependency>

准备属性配置文件jdbc.properties

jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306
jdbc.userName=root
jdbc.password=xiaohu

创建属性实体类来加载配置文件JdbcProperties

@Data
@Repository
@PropertySource(value = "classpath:jdbc.properties")
public class JdbcProperties {
    @Value("${jdbc.driver}")
    private String driver;
    @Value("${jdbc.url}")
    private String url;
    @Value("${jdbc.userName}")
    private String userName;
    @Value("${jdbc.password}")
    private String password;
}

创建JDBC配置类JdbcConfig

@Component
public class JdbcConfig {
    @Bean
    public DataSource dataSource(JdbcProperties jdbcProperties){
        System.out.println("打印获取到的配置信息:"+jdbcProperties);
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName(jdbcProperties.getDriver());
        dataSource.setUrl(jdbcProperties.getUrl());
        dataSource.setUsername(jdbcProperties.getUserName());
        dataSource.setPassword(jdbcProperties.getPassword());
        return dataSource;
    }
}

创建Spring配置类SpringConfiguration

@Configuration
public class SpringConfiguration {

}

创建测试类测试读取配置文件

public class PropertySourceTest {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext("config");
        DataSource dataSource = context.getBean("dataSource",DataSource.class);
        System.out.println(dataSource);
    }
}

查看输出结果:

打印获取到的配置信息:JdbcProperties(driver=com.mysql.cj.jdbc.Driver, url=jdbc:mysql://127.0.0.1:3306, userName=root, password=xiaohu)
org.springframework.jdbc.datasource.DriverManagerDataSource@58695725

从结果可以看出,我们的properties中的配置已经成功读取到,并且DataSource也从Spring容器中获取到。上面介绍注解的属性时,factory是4.3版本才加入的,那么如果4.3版本之前要解析配置文件又应该怎么处理呢?,这个时候就需要手动将解析配置文件的Bean注入到Spring容器中了,用法很简单,在SpringConfiguration类中添加如下代码即可:

@Bean
public PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer(){
    return new PropertySourcesPlaceholderConfigurer();
}

具体测试结果,就自行测试了。上面例子介绍了properties的使用,下面我们将配置文件换成xml文件。配置如下:

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
<properties>
    <entry key="jdbc.driver">com.mysql.cj.jdbc.Driver</entry>
    <entry key="jdbc.url">jdbc:mysql://127.0.0.1:3306/test</entry>
    <entry key="jdbc.userName">root</entry>
    <entry key="jdbc.password">xiaohu</entry>
</properties>

然后将JdbcProperties类上的注解的配置文件换成xml文件。

@PropertySource(value = "classpath:jdbc.properties")

其他不用调整,执行测试类,输出的结果一样。因为上面介绍到@PropertySource默认支持propertiesxml的配置文件。我们可以查看PropertySourceFactory的默认实现DefaultPropertySourceFactory源码

public class DefaultPropertySourceFactory implements PropertySourceFactory {

	@Override
	public PropertySource<?> createPropertySource(@Nullable String name, EncodedResource resource) throws IOException {
		return (name != null ? new ResourcePropertySource(name, resource) : new ResourcePropertySource(resource));
	}
}

然后进入ResourcePropertySource类,源码这里使用了一个三元运算符,如果name为空,就使用默认Spring默认生成的name

public ResourcePropertySource(String name, EncodedResource resource) throws IOException {
		super(name, PropertiesLoaderUtils.loadProperties(resource));
		this.resourceName = getNameForResource(resource.getResource());
	}
	
public ResourcePropertySource(EncodedResource resource) throws IOException {
		super(getNameForResource(resource.getResource()), PropertiesLoaderUtils.loadProperties(resource));
		this.resourceName = null;
	}

这里可以看到调用了PropertiesLoaderUtils.loadProperties方法,进入到源码

public static Properties loadProperties(EncodedResource resource) throws IOException {
	Properties props = new Properties();
	fillProperties(props, resource);
	return props;
}

会调用fillProperties的方法,一直跟到调用最低的fillProperties方法。

static void fillProperties(Properties props, EncodedResource resource, PropertiesPersister persister)
			throws IOException {
	InputStream stream = null;
	Reader reader = null;
	try {
		String filename = resource.getResource().getFilename();
		if (filename != null && filename.endsWith(XML_FILE_EXTENSION)) {
			stream = resource.getInputStream();
			persister.loadFromXml(props, stream);
		}
		else if (resource.requiresReader()) {
			reader = resource.getReader();
			persister.load(props, reader);
		}
		else {
			stream = resource.getInputStream();
			persister.load(props, stream);
		}
	}
	finally {
		if (stream != null) {
			stream.close();
		}
		if (reader != null) {
			reader.close();
		}
	}
}

第一个if判断文件后缀是否是xml结尾,常量XML_FILE_EXTENSION如下:

private static final String XML_FILE_EXTENSION = ".xml";

除了支持propertiesxml的配置文件方式,也支持yml配置文件的方式,不过需要自定义解析工厂,下面来实现怎么解析yml配置文件。引入可以解析yml文件的第三方库

<dependency>
    <groupId>org.yaml</groupId>
    <artifactId>snakeyaml</artifactId>
    <version>1.28</version>
</dependency>

创建yml解析工厂YamlPropertySourceFactory实现PropertySourceFactory

public class YamlPropertySourceFactory implements PropertySourceFactory {
    @Override
    public PropertySource<?> createPropertySource(String name, EncodedResource resource) throws IOException {
        YamlPropertiesFactoryBean factoryBean = new YamlPropertiesFactoryBean();
        factoryBean.setResources(resource.getResource());
        Properties properties = factoryBean.getObject();
        return name != null ? new PropertiesPropertySource(name, properties) : new PropertiesPropertySource(resource.getResource().getFilename(), properties);
    }
}

然后将JdbcProperties类的@PropertySource换成如下写法:

@PropertySource(value = "classpath:jdbc.yml",factory = YamlPropertySourceFactory.class)

执行测试类,输出结果与上面结果一样

打印获取到的配置信息:JdbcProperties(driver=com.mysql.cj.jdbc.Driver, url=jdbc:mysql://127.0.0.1:3306, userName=root, password=xiaohu)
org.springframework.jdbc.datasource.DriverManagerDataSource@58695725

证明我们自定义的解析yml配置文件就成功了。

标签:PropertySource,jdbc,resource,配置文件,Spring,properties,注解,public
来源: https://www.cnblogs.com/tenghu/p/15159414.html