JAVA reads Properties file
Method 1. Load the content in the configuration file jdbc.properties through context:property-placeholder
<context:property-placeholder location="classpath:jdbc.properties" ignore-unresolvable="true"/>
The above configuration is equivalent to the following configuration, which is a simplification of the following configuration
<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>
Note: In this way, if you have the following configuration in the spring-mvc.xml file, the red part below must not be missing.
<!-- Configure component scanning, only Controller annotations are scanned in the springmvc container--> <context:component-scan base-package="com.hafiz.www" use-default-filters="false"> <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/> </context:component-scan>
Method 2. Use annotation injection, mainly used in java code to use annotation to inject the corresponding value value in the properties file
<bean id="prop" class="org.springframework.beans.factory.config.PropertiesFactoryBean"> <!-- Here is the PropertiesFactoryBean class, which also has a locations property and also receives an array, the same as above --> <property name="locations"> <array> <value>classpath:jdbc.properties</value> </array> </property> </bean>
Method 3. Use the util:properties tag to expose the contents of the properties file
<util:properties id="propertiesReader" location="classpath:jdbc.properties"/>
Note: To use the above line of configuration, you need to declare the following red part at the head of the spring-dao.xml file
<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">
方式4.通过PropertyPlaceholderConfigurer在加载上下文的时候暴露properties到自定义子类的属性中以供程序中使用
<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>
自定义类PropertyConfigurer的声明如下:
package com.hafiz.www.util; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer; import java.util.Properties; 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); } }
使用方式:在需要使用的类中使用@Autowired注解注入即可。
方式5.自定义工具类PropertyUtil,并在该类的static静态代码块中读取properties文件内容保存在static属性中以供别的程序使用
package com.hafiz.www.util; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.io.*; import java.util.Properties; 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); } }
说明:这样的话,在该类被加载的时候,它就会自动读取指定位置的配置文件内容并保存到静态属性中,高效且方便,一次加载,可多次使用。