Java读取properties文件内容的几种方式详解

<context:property-placeholder location="classpath:jdbc.properties" 
ignore-unresolvable="true"/>

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
 <property name="ignoreUnresolvablePlaceholders" value="true"/>
 <property name="locations">
    <list>
       <value>classpath:jdbc.properties</value>
    </list>
 </property>
</bean>

<!-- 配置组件扫描，springmvc容器中只扫描Controller注解 -->
<context:component-scan base-package="com.zxt.www" use-default-filters="false">
 <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
</context:component-scan>

<util:properties id="propertiesReader" location="classpath:jdbc.properties"/>

<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns:context="http://www.springframework.org/schema/context"
 xmlns:util="http://www.springframework.org/schema/util"
 xsi:schemaLocation="http://www.springframework.org/schema/beans
 http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
 http://www.springframework.org/schema/context 
 http://www.springframework.org/schema/context/spring-context-3.2.xsd
 http://www.springframework.org/schema/util 
　　　　 http://www.springframework.org/schema/util/spring-util.xsd">

<bean id="propertyConfigurer" class="com.hafiz.www.util.PropertyConfigurer">
 <property name="ignoreUnresolvablePlaceholders" value="true"/>
 <property name="ignoreResourceNotFound" value="true"/>
 <property name="locations">
 <list>
 <value>classpath:jdbc.properties</value>
 </list>
 </property>
</bean>

/**
 * Desc:properties配置文件读取类
 */
public class PropertyConfigurer extends PropertyPlaceholderConfigurer {
	private Properties props; // 存取properties配置文件key-value结果
	@Override
	protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, Properties props)
			throws BeansException {
		super.processProperties(beanFactoryToProcess, props);
		this.props = props;
	}
	public String getProperty(String key){
		return this.props.getProperty(key);
	}
	public String getProperty(String key, String defaultValue) {
		return this.props.getProperty(key, defaultValue);
	}
	public Object setProperty(String key, String value) {
		return this.props.setProperty(key, value);
	}
}

/**
 * Desc:properties文件获取工具类
 */
public class PropertyUtil {
	private static final Logger logger = LoggerFactory.getLogger(PropertyUtil.class);
	private static Properties props;
	static{
		loadProps();
	}
	synchronized static private void loadProps(){
		logger.info("开始加载properties文件内容.......");
		props = new Properties();
		InputStream in = null;
		try {
			<!--第一种，通过类加载器进行获取properties文件流-->
			in = PropertyUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");
			<!--第二种，通过类进行获取properties文件流-->
			//in = PropertyUtil.class.getResourceAsStream("/jdbc.properties");
			props.load(in);
		} catch (FileNotFoundException e) {
			logger.error("jdbc.properties文件未找到");
		} catch (IOException e) {
			logger.error("出现IOException");
		} finally {
			try {
				if(null != in) {
					in.close();
				}
			} catch (IOException e) {
				logger.error("jdbc.properties文件流关闭出现异常");
			}
		}
		logger.info("加载properties文件内容完成...........");
		logger.info("properties文件内容：" + props);
	}
	public static String getProperty(String key){
		if(null == props) {
			loadProps();
		}
		return props.getProperty(key);
	}
	public static String getProperty(String key, String defaultValue) {
		if(null == props) {
			loadProps();
		}
		return props.getProperty(key, defaultValue);
	}
}

<bean id="prop" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
 <!--  这里是PropertiesFactoryBean类，它也有个locations属性，也是接收一个数组，跟上面一样 -->
 <property name="locations">
    <array>
      <value>classpath:jdbc.properties</value>
    </array>
 </property>
</bean>

string.port=1111
integer.port=1111

db.link.url=jdbc:mysql://localhost:3306/test
db.link.driver=com.mysql.jdbc.Driver
db.link.username=root
db.link.password=root

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

@Component
public class MyConf {

    @Value("${string.port}")     private int intPort;
    @Value("${string.port}")     private  String stringPort;
    @Value("${db.link.url}")     private String dbUrl;
    @Value("${db.link.driver}")  private String dbDriver;
    @Value("${db.link.username}")private String dbUsername;
    @Value("${db.link.password}")private String dbPassword;

    public void show(){
        System.out.println("======================================");
        System.out.println("intPort :   " + (intPort + 1111));
        System.out.println("stringPort :   " + (stringPort + 1111));
        System.out.println("string :   " + dbUrl);
        System.out.println("string :   " + dbDriver);
        System.out.println("string :   " + dbUsername);
        System.out.println("string :   " + dbPassword);
        System.out.println("======================================");
    }
}

@Value("${key}")
private Boolean timerEnabled;

@Autowired
private Environment environment;

@Setter
private Environment environment;

public boolean isDev(){
    boolean devFlag = environment.acceptsProfiles("dev");
    return  devFlag;
}

@Component
@ConfigurationProperties(prefix = "library")
class LibraryProperties {
 @NotEmpty
 private String location;
 private List<Book> books;

 @Setter
 @Getter
 @ToString
 static class Book {
  String name;
  String description;
 }
  //省略getter/setter
  ......
}

@Component
@PropertySource("classpath:website.properties")
class WebSite {
 @Value("${url}")
 private String url;
  省略getter/setter
  ......
}