读取properties文件内容

在现实工作中，我们常常需要保存一些系统配置信息，大家一般都会选择配置文件来完成，本文根据我工作中用到的读取properties配置文件的方法小小总结一下，主要叙述的是spring读取配置文件的方法。
   用spring读取配置文件,最典型的就是关于数据库的连接,下面就是一个例子:
   文件jdbc.properties:
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       driverClassName com.mysql.jdbc.Driver
       url jdbc:mysql://localhost:3306/test
       username root
       password 1234
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引入spring的相关jar包,在applicationContext.xml中配置:
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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">

<beans>
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location">
           <value>src/jdbc.properties</value>
</property>
</bean>

<bean id="datasource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName">
    <value>${driverClassName}</value>
</property>
<property name="url">
    <value>${url}</value>
</property>
<property name="username">
   <value>${username}</value>
</property>
<property name="password">
    <value>${password}</value>
</property>
</bean>

<bean id="dao" class="com.zh.model.DataDAO">
   <property name="datasource">
     <ref local="datasource"/>
   </property>
</bean>

</beans>
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DataDAO.java

package com.zh.model;

import javax.sql.DataSource;

public class DataDAO {
private DataSource datasource;

public DataSource getDatasource() {
return datasource;
}

public void setDatasource(DataSource datasource) {
this.datasource = datasource;
}

}
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测试连接是否成功,test.java
package com.zh.logic;

import java.sql.Connection;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;

import com.zh.model.DataDAO;

public class test {
public static void main(String [] args){
   try{
   String[] path = {"src/applicationContext.xml"};
   ApplicationContext ctx = new FileSystemXmlApplicationContext(path);

   DataDAO dao = (DataDAO)ctx.getBean("dao");
   Connection con = dao.getDatasource().getConnection();
   System.out.println(con.isClosed());
   //System.out.print(dao.getName());
   }catch(Exception ex){
   ex.printStackTrace();
     }
   }
}
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2.用java.util.Properties这个类来读取
比如，我们构造一个ipConfig.properties来保存服务器ip地址和端口，如：
ip=192.168.0.1
port=8080
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则，我们可以用如下程序来获得服务器配置信息：
InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream("ipConfig.properties");
   Properties p = new Properties();
   try{
       p.load(inputStream);
   } catch (IOException e1){
    e1.printStackTrace();
   }
System.out.println("ip:"+p.getProperty("ip")+",port:"+p.getProperty("port"));
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上面介绍了读取properties的内容,现实中我们还有可能要修改文件的内容,下面就看下怎么修改properties的内容,文件还是上面那个:
package com.zh.logic;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.util.Properties;

public class TestRead {
    
public void read(){
   try {
    InputStream in = this.getClass().getClassLoader().getResourceAsStream("config/host.properties");
    Properties p = new Properties();
    p.load(in);
    //p.list(System.out);
      
    System.out.println(p.getProperty("ip")+","+p.getProperty("username")+","+p.getProperty("pwd"));
   } catch (Exception e) {
    e.printStackTrace();
   }
}

public void update(String path){
    try{
     Properties p = new Properties();
     FileInputStream in = new FileInputStream(path);
     p.load(in);
     FileOutputStream out = new FileOutputStream(path);
    
     p.setProperty("ip","1234567");
     p.store(out,"ip update");
     //p.save(out,"ip updated");
    }catch(Exception ex){
     ex.printStackTrace();
    }
}
public static void main(String[] args){
   TestRead td = new TestRead();
   td.read();
   td.update("config/host.properties");
   td.read();
}
}
可以看见修改之前的和修改之后的内容有改变;在上面有点要注意的:
        FileInputStream in = new FileInputStream(path);
        p.load(in);
        FileOutputStream out = new FileOutputStream(path);
就是p.load(in);要写在FileOutputStream out = new FileOutputStream(path);之前,不然的话,修改后的文件内容就成了ip=1234567,而port=8080这句被覆盖了;什么愿意大家自己想想吧;