如何读取properties文件中属性

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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database.properties:
-------------------------------------------------------------------------------------
jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/zjgxm?charset=utf-8
jdbc.username=root
jdbc.password=111111

#
dataSource.initialSize=5
#
dataSource.maxIdle=0
#
dataSource.minIdle=5
#最大连接数量
dataSource.maxActive=50
#是否在自动回收超时连接的时候打印连接的超时错误
dataSource.logAbandoned=true
#是否自动回收超时连接
dataSource.removeAbandoned=true
#超时时间(以秒数为单位)
dataSource.removeAbandonedTimeout=180
#
dataSource.maxWait=1000
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引入spring的相关jar包,在applicationContext.xml中配置:
-------------------------------------------------------------------------------------

<?xml version="1.0" encoding="UTF-8"?><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:aop="http://www.springframework.org/schema/aop"        xmlns:tx="http://www.springframework.org/schema/tx"       xsi:schemaLocation="http://www.springframework.org/schema/beans        http://www.springframework.org/schema/beans/spring-beans-2.5.xsd        http://www.springframework.org/schema/context        http://www.springframework.org/schema/context/spring-context-2.5.xsdhttp://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop-2.5.xsd    http://www.springframework.org/schema/tx    http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">        <property name="locations">            <value>classpath:database.properties</value>        </property>    </bean>        <bean id="dataSource" destroy-method="close"          class="org.apache.commons.dbcp.BasicDataSource">        <property name="driverClassName" value="${jdbc.driverClassName}"/>        <property name="url" value="${jdbc.url}"/>        <property name="username" value="${jdbc.username}"/>        <property name="password" value="${jdbc.password}"/>                <property name="initialSize" value="${dataSource.initialSize}"/>        <property name="maxIdle" value="${dataSource.maxIdle}"/>        <property name="minIdle" value="${dataSource.minIdle}"/>        <property name="maxActive" value="${dataSource.maxActive}"/>        <property name="logAbandoned" value="${dataSource.logAbandoned}"/>        <property name="removeAbandoned" value="${dataSource.removeAbandoned}"/>        <property name="removeAbandonedTimeout" value="${dataSource.removeAbandonedTimeout}"/>        <property name="maxWait" value="${dataSource.maxWait}"/>    </bean>        <import resource="spring-conf/spring-admin.xml"/>    </beans>

-----------------------------------------------------------------------------------------
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;
}

}
------------------------------------------------------------------------------------
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 = {"spring.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();
}
}
}
-------------------------------------------------------------------------------------
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
--------------------------------------------------------------------------------------
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("database.properties");
Properties p = new Properties();
try{
p.load(inputStream);
} catch (IOException e1){
e1.printStackTrace();
}
System.out.println("url:"+p.getProperty("jdbc.url")+"username"+p.getProperty("jdbc.username"));
--------------------------------------------------------------------------------------
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;

方法3：

package com.util;import java.io.FileNotFoundException;import java.io.IOException;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import java.util.Properties;public class DBUtil {public static void main(String[] args){   DBUtil db = new DBUtil();   db.readProperties();    }public void readProperties(){   try {    Properties props = new Properties();    //第一种读取 properties 方法    props.load(getClass().getResourceAsStream("/config/oracleConn.properties"));           //-------------------------------------------------------------    //读取键值    String oracle_url = props.getProperty("oracle_url");    String oracle_name = props.getProperty("oracle_name");    String oracle_user = props.getProperty("oracle_user");    String oracle_pwd = props.getProperty("oracle_pwd");       Class.forName("oracle.jdbc.driver.OracleDriver"); //加载oracle驱动    Connection conn = DriverManager.getConnection(oracle_url,oracle_user,oracle_pwd);    System.out.println(conn);       conn.close();   } catch (FileNotFoundException e) {    e.printStackTrace();   } catch (IOException e) {    e.printStackTrace();   } catch (ClassNotFoundException e) {    e.printStackTrace();   } catch (SQLException e) {    e.printStackTrace();   }}}

引自：http://hi.baidu.com/alizv/item/358543e1b6ad2df32a09a426

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