社群 學習 工具庫 休閒
搜尋
繁体中文
首頁 > 後端開發 > XML/RSS教程 > Java&Xml教學（十）XML作為屬性檔使用

Java&Xml教學（十）XML作為屬性檔使用

黄舟
發布： 2017-02-22 14:58:35
原創
1900 人瀏覽過

我们通常会将Java应用的配置参数保存在属性文件中，Java应用的属性文件可以是一个正常的基于key-value对,以properties为扩展名的文件，也可以是XML文件. 

在本案例中，將会向大家介绍如何通过Java程序输出这两种格式的属性文件，并介绍如何从classpath中加载和使用这两种属性文件。
下面是案例程序代码：
PropertyFilesUtil.java

package com.journaldev.util;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import java.util.Set;
public class PropertyFilesUtil {

    public static void main(String[] args) throws IOException {
        String propertyFileName = "DB.properties";
        String xmlFileName = "DB.xml";
        writePropertyFile(propertyFileName, xmlFileName);
        readPropertyFile(propertyFileName, xmlFileName);
        readAllKeys(propertyFileName, xmlFileName);
        readPropertyFileFromClasspath(propertyFileName);
    }    /**
     * read property file from classpath
     * @param propertyFileName
     * @throws IOException
     */
    private static void readPropertyFileFromClasspath(String propertyFileName) throws IOException {
        Properties prop = new Properties();
        prop.load(PropertyFilesUtil.class.getClassLoader().getResourceAsStream(propertyFileName));
        System.out.println(propertyFileName +" loaded from Classpath::db.host = "+prop.getProperty("db.host"));
        System.out.println(propertyFileName +" loaded from Classpath::db.user = "+prop.getProperty("db.user"));
        System.out.println(propertyFileName +" loaded from Classpath::db.pwd = "+prop.getProperty("db.pwd"));
        System.out.println(propertyFileName +" loaded from Classpath::XYZ = "+prop.getProperty("XYZ"));

    }    /**
     * read all the keys from the given property files
     * @param propertyFileName
     * @param xmlFileName
     * @throws IOException 
     */
    private static void readAllKeys(String propertyFileName, String xmlFileName) throws IOException {
        System.out.println("Start of readAllKeys");
        Properties prop = new Properties();
        FileReader reader = new FileReader(propertyFileName);
        prop.load(reader);
        Set<Object> keys= prop.keySet();        for(Object obj : keys){
            System.out.println(propertyFileName + ":: Key="+obj.toString()+"::value="+prop.getProperty(obj.toString()));
        }        //loading xml file now, first clear existing properties
        prop.clear();
        InputStream is = new FileInputStream(xmlFileName);
        prop.loadFromXML(is);
        keys= prop.keySet();        for(Object obj : keys){
            System.out.println(xmlFileName + ":: Key="+obj.toString()+"::value="+prop.getProperty(obj.toString()));
        }        //Now free all the resources
        is.close();
        reader.close();
        System.out.println("End of readAllKeys");
    }    /**
     * This method reads property files from file system
     * @param propertyFileName
     * @param xmlFileName
     * @throws IOException 
     * @throws FileNotFoundException 
     */
    private static void readPropertyFile(String propertyFileName, String xmlFileName) throws FileNotFoundException, IOException {
        System.out.println("Start of readPropertyFile");
        Properties prop = new Properties();
        FileReader reader = new FileReader(propertyFileName);
        prop.load(reader);
        System.out.println(propertyFileName +"::db.host = "+prop.getProperty("db.host"));
        System.out.println(propertyFileName +"::db.user = "+prop.getProperty("db.user"));
        System.out.println(propertyFileName +"::db.pwd = "+prop.getProperty("db.pwd"));
        System.out.println(propertyFileName +"::XYZ = "+prop.getProperty("XYZ"));        
        //loading xml file now, first clear existing properties
        prop.clear();
        InputStream is = new FileInputStream(xmlFileName);
        prop.loadFromXML(is);
        System.out.println(xmlFileName +"::db.host = "+prop.getProperty("db.host"));
        System.out.println(xmlFileName +"::db.user = "+prop.getProperty("db.user"));
        System.out.println(xmlFileName +"::db.pwd = "+prop.getProperty("db.pwd"));
        System.out.println(xmlFileName +"::XYZ = "+prop.getProperty("XYZ"));        
        //Now free all the resources
        is.close();
        reader.close();
        System.out.println("End of readPropertyFile");
    }    /**
     * This method writes Property files into file system in property file
     * and xml format
     * @param fileName
     * @throws IOException
     */
    private static void writePropertyFile(String propertyFileName, String xmlFileName) throws IOException {
        System.out.println("Start of writePropertyFile");
        Properties prop = new Properties();
        prop.setProperty("db.host", "localhost");
        prop.setProperty("db.user", "user");
        prop.setProperty("db.pwd", "password");
        prop.store(new FileWriter(propertyFileName), "DB Config file");
        System.out.println(propertyFileName + " written successfully");
        prop.storeToXML(new FileOutputStream(xmlFileName), "DB Config XML file");
        System.out.println(xmlFileName + " written successfully");
        System.out.println("End of writePropertyFile");
    }

}
登入後複製
登入後複製

当运行这段代码时，writePropertyFile 方法会在生成上述两种格式的属性文件，并將文件存储在工程的根目录下。
writePropertyFile 方法生成的两种属性文件内容：
DB.properties

#DB Config file#Fri Nov 16 11:16:37 PST 2012db.user=user
db.host=localhost
db.pwd=password
登入後複製
登入後複製

DB.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?><!DOCTYPE properties SYSTEM 
"http://java.sun.com/dtd/properties.dtd"><properties><comment>DB Config XML file</comment>
<entry key="db.user">user</entry><entry key="db.host">localhost</entry><entry key="db.pwd">password</entry>
</properties>
登入後複製

需要注意的是comment元素，我们在使用prop.storeToXML(new FileOutputStream(xmlFileName), "DB Config XML file");这段代码时第二个参数传入的是注释内容，如果传入null，生成的xml属性文件將没有comment元素。
控制台输出内容如下：

Start of writePropertyFile
DB.properties written successfully
DB.xml written successfully
End of writePropertyFile
Start of readPropertyFileDB.properties::db.host = localhostDB.properties::db.user = 
userDB.properties::db.pwd = passwordDB.properties::XYZ = nullDB.xml::db.host = 
localhostDB.xml::db.user = userDB.xml::db.pwd = passwordDB.xml::XYZ = null
End of readPropertyFile
Start of readAllKeysDB.properties:: Key=db.user::value=userDB.properties:: 
Key=db.host::value=localhostDB.properties:: Key=db.pwd::value=passwordDB.xml:: Key=db.user::value=userDB.xml:: 
Key=db.host::value=localhostDB.xml:: Key=db.pwd::value=password
End of readAllKeys
Exception in thread "main" java.lang.NullPointerException
    at java.util.Properties$LineReader.readLine(Properties.java:434)
    at java.util.Properties.load0(Properties.java:353)
    at java.util.Properties.load(Properties.java:341)
    at com.journaldev.util.PropertyFilesUtil.readPropertyFileFromClasspath(PropertyFilesUtil.java:31)
    at com.journaldev.util.PropertyFilesUtil.main(PropertyFilesUtil.java:21)
登入後複製

这里报了空指针异常，原因是生成的文件保存在工程的根目录下面，而读取时是从classpath下读取，將上面生成的两个属性文件拷贝到src下再次运行程序即可。

我们通常会将Java应用的配置参数保存在属性文件中，Java应用的属性文件可以是一个正常的基于key-value对,以properties为扩展名的文件，也可以是XML文件.
在本案例中，將会向大家介绍如何通过Java程序输出这两种格式的属性文件，并介绍如何从classpath中加载和使用这两种属性文件。
下面是案例程序代码：
PropertyFilesUtil.java

package com.journaldev.util;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import java.util.Set;
public class PropertyFilesUtil {

    public static void main(String[] args) throws IOException {
        String propertyFileName = "DB.properties";
        String xmlFileName = "DB.xml";
        writePropertyFile(propertyFileName, xmlFileName);
        readPropertyFile(propertyFileName, xmlFileName);
        readAllKeys(propertyFileName, xmlFileName);
        readPropertyFileFromClasspath(propertyFileName);
    }    /**
     * read property file from classpath
     * @param propertyFileName
     * @throws IOException
     */
    private static void readPropertyFileFromClasspath(String propertyFileName) throws IOException {
        Properties prop = new Properties();
        prop.load(PropertyFilesUtil.class.getClassLoader().getResourceAsStream(propertyFileName));
        System.out.println(propertyFileName +" loaded from Classpath::db.host = "+prop.getProperty("db.host"));
        System.out.println(propertyFileName +" loaded from Classpath::db.user = "+prop.getProperty("db.user"));
        System.out.println(propertyFileName +" loaded from Classpath::db.pwd = "+prop.getProperty("db.pwd"));
        System.out.println(propertyFileName +" loaded from Classpath::XYZ = "+prop.getProperty("XYZ"));

    }    /**
     * read all the keys from the given property files
     * @param propertyFileName
     * @param xmlFileName
     * @throws IOException 
     */
    private static void readAllKeys(String propertyFileName, String xmlFileName) throws IOException {
        System.out.println("Start of readAllKeys");
        Properties prop = new Properties();
        FileReader reader = new FileReader(propertyFileName);
        prop.load(reader);
        Set<Object> keys= prop.keySet();        for(Object obj : keys){
            System.out.println(propertyFileName + ":: Key="+obj.toString()+"::value="+prop.getProperty(obj.toString()));
        }        //loading xml file now, first clear existing properties
        prop.clear();
        InputStream is = new FileInputStream(xmlFileName);
        prop.loadFromXML(is);
        keys= prop.keySet();        for(Object obj : keys){
            System.out.println(xmlFileName + ":: Key="+obj.toString()+"::value="+prop.getProperty(obj.toString()));
        }        //Now free all the resources
        is.close();
        reader.close();
        System.out.println("End of readAllKeys");
    }    /**
     * This method reads property files from file system
     * @param propertyFileName
     * @param xmlFileName
     * @throws IOException 
     * @throws FileNotFoundException 
     */
    private static void readPropertyFile(String propertyFileName, String xmlFileName) throws FileNotFoundException, IOException {
        System.out.println("Start of readPropertyFile");
        Properties prop = new Properties();
        FileReader reader = new FileReader(propertyFileName);
        prop.load(reader);
        System.out.println(propertyFileName +"::db.host = "+prop.getProperty("db.host"));
        System.out.println(propertyFileName +"::db.user = "+prop.getProperty("db.user"));
        System.out.println(propertyFileName +"::db.pwd = "+prop.getProperty("db.pwd"));
        System.out.println(propertyFileName +"::XYZ = "+prop.getProperty("XYZ"));        
        //loading xml file now, first clear existing properties
        prop.clear();
        InputStream is = new FileInputStream(xmlFileName);
        prop.loadFromXML(is);
        System.out.println(xmlFileName +"::db.host = "+prop.getProperty("db.host"));
        System.out.println(xmlFileName +"::db.user = "+prop.getProperty("db.user"));
        System.out.println(xmlFileName +"::db.pwd = "+prop.getProperty("db.pwd"));
        System.out.println(xmlFileName +"::XYZ = "+prop.getProperty("XYZ"));        
        //Now free all the resources
        is.close();
        reader.close();
        System.out.println("End of readPropertyFile");
    }    /**
     * This method writes Property files into file system in property file
     * and xml format
     * @param fileName
     * @throws IOException
     */
    private static void writePropertyFile(String propertyFileName, String xmlFileName) throws IOException {
        System.out.println("Start of writePropertyFile");
        Properties prop = new Properties();
        prop.setProperty("db.host", "localhost");
        prop.setProperty("db.user", "user");
        prop.setProperty("db.pwd", "password");
        prop.store(new FileWriter(propertyFileName), "DB Config file");
        System.out.println(propertyFileName + " written successfully");
        prop.storeToXML(new FileOutputStream(xmlFileName), "DB Config XML file");
        System.out.println(xmlFileName + " written successfully");
        System.out.println("End of writePropertyFile");
    }

}
登入後複製
登入後複製

当运行这段代码时，writePropertyFile 方法会在生成上述两种格式的属性文件，并將文件存储在工程的根目录下。
writePropertyFile 方法生成的两种属性文件内容：
DB.properties

#DB Config file#Fri Nov 16 11:16:37 PST 2012db.user=user
db.host=localhost
db.pwd=password
登入後複製
登入後複製

DB.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?><!DOCTYPE properties SYSTEM " 
<properties><comment>DB Config XML file</comment><entry key="db.user">user</entry><entry key="db.host">localhost</entry>
<entry key="db.pwd">password</entry></properties>
登入後複製

需要注意的是comment元素，我们在使用prop.storeToXML(new FileOutputStream(xmlFileName), "DB Config XML file");这段代码时第二个参数传入的是注释内容，如果传入null，生成的xml属性文件將没有comment元素。
控制台输出内容如下：

Start of writePropertyFile
DB.properties written successfully
DB.xml written successfully
End of writePropertyFile
Start of readPropertyFileDB.properties::db.host = localhostDB.properties::db.user = userDB.properties::db.pwd = passwordDB.properties::XYZ = 
nullDB.xml::db.host = localhostDB.xml::db.user = userDB.xml::db.pwd = passwordDB.xml::XYZ = null
End of readPropertyFile
Start of readAllKeysDB.properties:: Key=db.user::value=userDB.properties:: Key=db.host::value=localhostDB.properties:: Key=db.pwd::value=passwordDB.xml:: 
Key=db.user::value=userDB.xml:: Key=db.host::value=localhostDB.xml:: Key=db.pwd::value=password
End of readAllKeys
Exception in thread "main" java.lang.NullPointerException
    at java.util.Properties$LineReader.readLine(Properties.java:434)
    at java.util.Properties.load0(Properties.java:353)
    at java.util.Properties.load(Properties.java:341)
    at com.journaldev.util.PropertyFilesUtil.readPropertyFileFromClasspath(PropertyFilesUtil.java:31)
    at com.journaldev.util.PropertyFilesUtil.main(PropertyFilesUtil.java:21)
登入後複製

以上就是Java&Xml教程（十）XML作为属性文件使用的内容，更多相关内容请关注PHP中文网（www.php.cn）！


相關標籤：
屬性檔案
來源：php.cn
上一篇：Java&Xml教學（八）使用JDOM將Java物件轉換為XML 下一篇：Java物件、Json、Xml轉換工具Jackson使用
本網站聲明
本文內容由網友自願投稿，版權歸原作者所有。本站不承擔相應的法律責任。如發現涉嫌抄襲或侵權的內容，請聯絡admin@php.cn
作者最新文章
最新問題
SimpleXML 未載入 GML 數據 我有以下範例XML數據，我想使用PHP將其解析為SimpleXML：<?xmlversion="1.0"encoding="utf-8"...
來自於 2024-04-04 10:04:41
0
1
358
使用 simplexml_load_file() php，XML RSS 的標題出現 JP 字元錯誤 PHP版本：7.4.30我使用simplexml_load_filephp函數，$rss=simplexml_load_file($url,'SimpleXMLElement',L...
來自於 2024-04-03 21:22:05
0
1
304
如何從資料庫中取得所有值並返回XML欄位中的PHP程式碼？ 我的應用程式需要一些幫助。我有這個程式碼：即時.php$jogador=Jogador::getSaldoJogadorByEmail($email);$premio=Premio...
來自於 2024-03-30 16:09:24
0
1
397
如何在javaScript中將字串轉換為19位數字而不自動舍入？ 我們有字串輸入數字輸入=“6145390195186705543”如果我們想轉換為數字；java腳本自動舍入此輸入；(6145390195186705543)(6145390195...
來自於 2024-03-30 14:42:35
0
1
367
相關專題
更多>
熱門推薦
熱門教學
更多>
相關教學
熱門推薦
最新課程
最新下載
更多>
網站特效
網站源碼
網站素材
前端模板