Described below is an efficient way of reading configurations from property files in a web application. It uses a class called AppConfigMaster to read all property files available at a directory location specified as a JVM argument. All key value pairs read from the property files are fed into a HashMap object, which is defined as a data member of the AppConfigMaster class. A singleton of this AppConfigMaster is maintained in the JVM so that the properties are read from the file system only once in a JVMs lifecycle.
AppConfigMaster.java
public class AppConfigMaster {
private static AppConfigMaster AppConfigMasterObj;
private Map configPropertiesMap = new HashMap();
public static String configurationFilesPath = null;
AppConfigMaster() throws SystemException {
try {
configurationFilesPath = System.getProperty("ApplicationConfigPath");
navigateConfigDirectory(configurationFilesPath);
} catch (Exception ex) {
//Do Something}
}
public synchronized static AppConfigMaster getInstance() {
if (AppConfigMasterObj == null) {
try {
AppConfigMasterObj = new AppConfigMaster();
} catch (SystemException e) {
e.printStackTrace();
}
}
return AppConfigMasterObj;
}
private void navigateConfigDirectory(String path) throws SystemException {
File configurationDirectiory = new File(path);
File[] subdirectories = null;
if ((configurationDirectiory.isDirectory())
&& (configurationDirectiory.exists())) {
subdirectories = configurationDirectiory.listFiles();
FilenameFilter propertiesFileFilter = new OnlyExt("properties");
int configDirLength = configurationDirectiory.listFiles(propertiesFileFilter).length;
for(int i=0;i
propertiesFileProcessor(configurationDirectiory.listFiles(propertiesFileFilter)[i]);
/*
* Assuming there are just 2 levels of nesting
*/
for (int i = 0; i < subdirectories.length; i++) {
if (subdirectories[i].isDirectory()) {
for (int j = 0; j < subdirectories[i].list(propertiesFileFilter).length; j++) {
propertiesFileProcessor(subdirectories[i].listFiles(propertiesFileFilter)[j]);
}
}
}
}
}
class OnlyExt implements FilenameFilter {
String ext;
public OnlyExt(String ext) {
this.ext = "." + ext;
}
public boolean accept(File dir, String name) {
return name.endsWith(ext);
}
}
private void propertiesFileProcessor(File file) throws SystemException {
Properties configProprties = new Properties();
FileInputStream inputstream;
String key = null;
String value = null;
try {
inputstream = new FileInputStream(file.getAbsolutePath());
configProprties.load(inputstream);
Enumeration keys = configProprties.keys();
while (keys.hasMoreElements()) {
key = (String) keys.nextElement();
value = configProprties.getProperty(key.toString());
configPropertiesMap.put(key, value);
}
} catch (FileNotFoundException e) {
//Do Something
} catch (IOException e) {
//Do Something
} catch (Exception e) {
//Do Something
}
}
public String getPropertyforkey(String key) {
try {
if (configPropertiesMap.containsKey(key))
return configPropertiesMap.get(key).toString();
else
//Do Something
} catch (ClassCastException cex) {
//Do Something
} catch (NullPointerException npex) {
//Do Something
}
return null;
}
public String reloadProperties() throws SystemException {
String retMessage = null;
try {
navigateConfigDirectory(configurationFilesPath);
retMessage = "Reload of properties Successful";
} catch (SystemException ex) {
retMessage = "Reload of properties unsuccessful";
//Do Something
}
return retMessage;
}
}
The class is then used in other class files that need to read key values from property file as below:
AppConfigMaster.getInstance().getPropertyforkey("artbody.html.imagespanclasss.right");
To use it in JSP files without using scriplets following additional wrapper class and tag file are used:
AppConfigUtil.java
public class AppconfigUtil {
private String key;
private String value;
public void setKey(String key) {
this.key = key;
}
public String getValue() {
value = AppConfigMaster.getInstance().getPropertyforkey(key);
value = (value == null)?"":value;
return value;
}
}
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean"%>
<%@ tag import="com.util.AppconfigUtil"%>
<%@ attribute name="property" required="true"%>
<%@ attribute name="id" required="true"%>
<jsp:useBean id="appconfig" class="com.util.AppconfigUtil">
<jsp:setProperty name="appconfig" property="key" value="${property}" />
jsp:useBean>
<bean:define id="value" name="appconfig" property="value" />
<%request.setAttribute(id,value);%>
Usage in a JSP file is illustrated below
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib tagdir="/WEB-INF/tags" prefix="appConfig"%>
<appConfig:getProperty property="site.url" id="site_url"/>
<b><c:out value="${site_url}"/></b>
NOTE
To prevent key name conflicts, all key names used in various property files should follow some agreed naming convention. Name space conflicts can cause logical errors otherwise.
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