String title = JiveGlobals.getJiveProperty("websiteconf.name"); //网页标题
进到JiveGlobals看一看
public static String getJiveProperty(String name) {
loadProperties();
return properties.getProperty(name);
}
看一看 loadProperties();
private synchronized static void loadProperties() {
if (jiveHome == null) {
jiveHome = new InitPropLoader().getJiveHome();
}
//Create a manager with the full path to the xml config file.
properties = new XMLProperties(jiveHome + File.separator +
JIVE_CONFIG_FILENAME);
}
package com.jivesoftware.forum.util;
import java.io.*;
import java.text.*;
import java.util.*;
import org.jdom.*;
import org.jdom.input.*;
import org.jdom.output.*;
/**
* Provides the the ability to use simple XML property files. Each property is
* in the form X.Y.Z, which would map to an XML snippet of:
* <pre>
* <X>
* <Y>
* <Z>someValue</Z>
* </Y>
* </X>
* </pre>
*
* The XML file is passed in to the constructor and must be readable and
* writtable. Setting property values will automatically persist those value
* to disk.
*/
public class XMLProperties {
private File file;
private Document doc;
/**
* Parsing the XML file every time we need a property is slow. Therefore,
* we use a Map to cache property values that are accessed more than once.
*/
private Map propertyCache = new HashMap();
/**
* Creates a new XMLProperties object.
*
* @parm file the full path the file that properties should be read from
* and written to.
*/
public XMLProperties(String file) {
this.file = new File(file);
try {
SAXBuilder builder = new SAXBuilder();
// Strip formatting
DataUnformatFilter format = new DataUnformatFilter();
builder.setXMLFilter(format);
doc = builder.build(new File(file));
}
catch (Exception e) {
System.err.println("Error creating XML parser in "
+ "PropertyManager.java");
e.printStackTrace();
}
}
/**
* Returns the value of the specified property.
*
* @param name the name of the property to get.
* @return the value of the specified property.
*/
public String getProperty(String name) {
if (propertyCache.containsKey(name)) {
return (String)propertyCache.get(name);
}
String[] propName = parsePropertyName(name);
// Search for this property by traversing down the XML heirarchy.
Element element = doc.getRootElement();
for (int i = 0; i < propName.length; i++) {
element = element.getChild(propName[i]);
if (element == null) {
// This node doesn't match this part of the property name which
// indicates this property doesn't exist so return null.
return null;
}
}
// At this point, we found a matching property, so return its value.
// Empty strings are returned as null.
String value = element.getText();
if ("".equals(value)) {
return null;
}
else {
// Add to cache so that getting property next time is fast.
value = value.trim();
propertyCache.put(name, value);
return value;
}
}
/**
* Return all children property names of a parent property as a String array,
* or an empty array if the if there are no children. For example, given
* the properties <tt>X.Y.A</tt>, <tt>X.Y.B</tt>, and <tt>X.Y.C</tt>, then
* the child properties of <tt>X.Y</tt> are <tt>A</tt>, <tt>B</tt>, and
* <tt>C</tt>.
*
* @param parent the name of the parent property.
* @return all child property values for the given parent.
*/
public String [] getChildrenProperties(String parent) {
String[] propName = parsePropertyName(parent);
// Search for this property by traversing down the XML heirarchy.
Element element = doc.getRootElement();
for (int i = 0; i < propName.length; i++) {
element = element.getChild(propName[i]);
if (element == null) {
// This node doesn't match this part of the property name which
// indicates this property doesn't exist so return empty array.
return new String [] { };
}
}
// We found matching property, return names of children.
List children = element.getChildren();
int childCount = children.size();
String [] childrenNames = new String[childCount];
for (int i=0; i<childCount; i++) {
childrenNames[i] = ((Element)children.get(i)).getName();
}
return childrenNames;
}
/**
* Sets the value of the specified property. If the property doesn't
* currently exist, it will be automatically created.
*
* @param name the name of the property to set.
* @param value the new value for the property.
*/
public void setProperty(String name, String value) {
// Set cache correctly with prop name and value.
propertyCache.put(name, value);
String[] propName = parsePropertyName(name);
// Search for this property by traversing down the XML heirarchy.
Element element = doc.getRootElement();
for (int i=0; i<propName.length; i++) {
// If we don't find this part of the property in the XML heirarchy
// we add it as a new node
if (element.getChild(propName[i]) == null) {
element.addContent(new Element(propName[i]));
}
element = element.getChild(propName[i]);
}
// Set the value of the property in this node.
element.setText(value);
// write the XML properties to disk
saveProperties();
}
/**
* Deletes the specified property.
*
* @param name the property to delete.
*/
public void deleteProperty(String name) {
String[] propName = parsePropertyName(name);
// Search for this property by traversing down the XML heirarchy.
Element element = doc.getRootElement();
for (int i=0; i<propName.length-1; i++) {
element = element.getChild(propName[i]);
// Can't find the property so return.
if (element == null) {
return;
}
}
// Found the correct element to remove, so remove it...
element.removeChild(propName[propName.length-1]);
// .. then write to disk.
saveProperties();
}
/**
* Saves the properties to disk as an XML document. A temporary file is
* used during the writing process for maximum safety.
*/
private synchronized void saveProperties() {
OutputStream out = null;
boolean error = false;
// Write data out to a temporary file first.
File tempFile = null;
try {
tempFile = new File(file.getParentFile(), file.getName() + ".tmp");
// Use JDOM's XMLOutputter to do the writing and formatting. The
// file should always come out pretty-printed.
XMLOutputter outputter = new XMLOutputter(" ", true);
out = new BufferedOutputStream(new FileOutputStream(tempFile));
outputter.output(doc, out);
}
catch (Exception e) {
e.printStackTrace();
// There were errors so abort replacing the old property file.
error = true;
}
finally {
try { out.close(); }
catch (Exception e) {
e.printStackTrace();
error = true;
}
}
// No errors occured, so we should be safe in replacing the old
if (!error) {
// Delete the old file so we can replace it.
file.delete();
// Rename the temp file. The delete and rename won't be an
// automic operation, but we should be pretty safe in general.
// At the very least, the temp file should remain in some form.
tempFile.renameTo(file);
}
}
/**
* Returns an array representation of the given Jive property. Jive
* properties are always in the format "prop.name.is.this" which would be
* represented as an array of four Strings.
*
* @param name the name of the Jive property.
* @return an array representation of the given Jive property.
*/
private String[] parsePropertyName(String name) {
// Figure out the number of parts of the name (this becomes the size
// of the resulting array).
int size = 1;
for (int i=0; i<name.length(); i++) {
if (name.charAt(i) == '.') {
size++;
}
}
String[] propName = new String[size];
// Use a StringTokenizer to tokenize the property name.
StringTokenizer tokenizer = new StringTokenizer(name, ".");
int i = 0;
while (tokenizer.hasMoreTokens()) {
propName[i] = tokenizer.nextToken();
i++;
}
return propName;
}
}
著名的Open Source论坛Jive有很多东西值得我们分析和学习,通过分析其Jdom的使用机制,我们可以自如方便的读写XML配置文件,从而实现下列一些功能:
1.,在配置文件中设置系统语言版本属性,不同语言版本,系统界面文字不一样,可以定义自己国家的文字,比如英文版 中文简体版. 这样,可以很方便的将一个系统延伸到各种语言,不用直接修改程序,只要修改XML配置文件就可以.
2.在配置文件中设置邮件内容, 通常一个系统都有各种自动邮件分发,比如用户注册成功后,会有一封Email发送到他的信箱,这套系统安装在不同客户场合,Email的内容当然不一样,如A客户使用了这套系统,当然希望在Email中有A客户的单位名称,这些都不必修改程序可以完成.
3.设置系统的可选属性,一个系统安装在不同客户场合中,客户的要求总有些不一样,有些功能是可选的,那么当然这些都要设置在XML配置文件中.
4.使用XML存放树形结构记录是最方便的,尤其对于那些目录分类系统,如Yahoo,在大分类中有小分类,或者直接是元素,
我们知道关系数据库是不擅长存放树形数据,在关系数据库中,典型做法是采取两个表:一个表记录每个cell;一个表指明其前后关系;但是我们一旦要从这两张表展开树形结构,将要在空间和时间上反复平衡.
如果使用XML作为数据源,就很方便解决这个问题,如果配合对XML数据源有很方便的增 修 删 等功能,那么我们当然选择XML,实际上,Jdom就方便地提供了这个工具.Jdom是类似DOM SAX之类的XML解析办法,只适合Java语言,Jdom的特点就是简单方便。
那么,让我们来看看Jive是怎么实现上面功能的吧,它是把这些属性都写在一个叫jive_config.xml的文件中.这个XML文件的排列方式和使用方式是这样:
XML文件内容格式:
|
<!-- root element, all properties must be under this element -->
<jive>
<email>
<fromName>Jive_Administrator</fromName>
<fromEmail>webmaster@example.com</fromEmail>
<subject>Your thread was updated!</subject>
<body>Hello {name}! The thread {threadName} was updated!</body>
</email>
<jive>
|
<jive></jive>是根元素,所有的属性必须在其中
使用方式也比较简单,使用标点符号"."来间隔.比如我们要得到上面的webmaster@example.com的值,那么使用email.fromEmail就可以.在Jive中,具体语句就是JiveGlobals.getJiveProperty("email.fromEmail");
这样获取值很简单,而且明了,无论XML树形结构有多深,我们都可以方便的获取.
这里关键的是一个使用Jdom来解析XML文件的类：XMLProperties 其中实现了几个主要操作方法：
获得(查询):getProperty(name) ；
新增修改:properties.setProperty(name, value)；
删除:properties.deleteProperty(name) ；
这几个方法是不是很类似Hasntable的方法？Hashtable中数据是存放在内存中，而XML是存放在文件系统，无疑我们可以象使用hashtable一样方便的使用XML。
XMLProperties我们可以原封不动的拷贝到我们系统中。唯一要做的就是编制类似Jive的JiveGlobals,其实这也很简单，分两步:先load取出XML文件；然后就提供getProperty(name)等方法。如
|
public class JiveGlobals {
private static final String JIVE_CONFIG_FILENAME = "jive_config.xml";
....
public static String getJiveProperty(String name) {
loadProperties();
return properties.getProperty(name);
}
....
private synchronized static void loadProperties() {
if (properties == null) {
//Create a manager with the full path to the xml config file.
properties = new XMLProperties(jiveHome + File.separator +
JIVE_CONFIG_FILENAME);
}
}
}
|