Properties类的用法

在java.util包下面有一个类Properties，该类主要用于读取以项目的配置文件（以．properties结尾的文件和xml文件）。

一. Properties结构

类继承结构如下:

class Properties extends Hashtable<Object,Object>

从上面可以看出来Properties继承自Hashtable。

二. 具体案例

案例一: 读取.properties文件。

首先建立一个.properties文件，内容如下：

#网站信息
website = http://www.swiftlet.net
author = admin
date = 2015年

java类如下:

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Properties;

public class ReadProperties
{
    public static void main(String[] args)
    {
        File file = new File("c:\\test.properties");
        FileInputStream in = null;
        try
        {
            in = new FileInputStream(file);
        }
        catch (FileNotFoundException e)
        {
            e.printStackTrace();
        }
        Properties p = new Properties();
        try
        {
            p.load(in);
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        p.list(System.out);
    }
}

输出结果如下:

aaarticlea/png;base64,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" alt="" />

案例二: 读取.xml文件。

首先建立一个.xml文件，内容如下：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
<properties>
<entry key="website">swiftlet.net</entry>
<entry key="author">admin</entry>
</properties>

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Properties;

public class ReadXml
{
    public static void main(String[] args)
    {

        File file = new File("c:\\test.xml");
        FileInputStream in = null;
        try
        {
            in = new FileInputStream(file);
        }
        catch (FileNotFoundException e)
        {
            e.printStackTrace();
        }
        Properties p = new Properties();
        try
        {
            p.loadFromXML(in);
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        p.list(System.out);
    }
}

输出结果如下:

aaarticlea/png;base64,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" alt="" />

三. 常见问题：

Invalid byte 1 of 1-byte UTF-8 sequence. 产生这个异常的原因是：
所读的xml文件实际是GBK或者其他编码的，而xml内容中却用<?xml version="1.0" encoding="utf-8"?>指定编码为utf-8，所以就报异常了！常见的解决访问有两种：
第一：可以直接在XML文件中更改UTF-8为GBK或GB2312
         <?xml   version="1.0"   encoding="GB2312"?>
第二：将xml文件的编码格式修改为utf-8重新保存一下就可以了。