读取properties文件 并解析占位符(借用hibernate代码)
把hibernate中读取properties文件的代码抽取出来了，直接贴代码：java:
package redolvePlaceHolder;import java.io.IOException;import java.io.InputStream;import java.util.Iterator;import java.util.Map;import java.util.Properties;import java.util.Map.Entry;/** * 此类借用了hibernate读取properties文件的代码， * 可以解析占位符比如$ * @author afei * */public class TestMain {private static final String PLACEHOLDER_START = "${";private static Properties pro;public static void main(String[] args) {try {pro=buildProperty("afei.properties");resolvePlaceHolders(pro);printProperties(pro);} catch (IOException e) {e.printStackTrace();}}public static void printProperties(Properties p){Iterator it=p.entrySet().iterator();while(it.hasNext()){Entry ent=(Entry)it.next();System.out.println(ent.getKey()+" : "+ent.getValue());}}/** * 解析占位符 * @param properties */public static void resolvePlaceHolders(Properties properties) {Iterator itr = properties.entrySet().iterator();while ( itr.hasNext() ) {final Map.Entry entry = ( Map.Entry ) itr.next();final Object value = entry.getValue();if ( value != null && String.class.isInstance( value ) ) {final String resolved = resolvePlaceHolder( ( String ) value );if ( !value.equals( resolved ) ) {if ( resolved == null ) {itr.remove();}else {entry.setValue( resolved );}}}}}/** * 解析占位符具体操作 * @param property * @return */public static String resolvePlaceHolder(String property) {if ( property.indexOf( PLACEHOLDER_START ) < 0 ) {return property;}StringBuffer buff = new StringBuffer();char[] chars = property.toCharArray();for ( int pos = 0; pos < chars.length; pos++ ) {if ( chars == '$' ) {// peek aheadif ( chars == '{' ) {// we have a placeholder, spin forward till we find the endString systemPropertyName = "";int x = pos + 2;for (; x < chars.length && chars != '}'; x++ ) {systemPropertyName += chars;// if we reach the end of the string w/o finding the// matching end, that is an exceptionif ( x == chars.length - 1 ) {throw new IllegalArgumentException( "unmatched placeholder start [" + property + "]" );}}String systemProperty = extractFromSystem( systemPropertyName );buff.append( systemProperty == null ? "" : systemProperty );pos = x + 1;// make sure spinning forward did not put us past the end of the buffer...if ( pos >= chars.length ) {break;}}}buff.append( chars );}String rtn = buff.toString();return isEmpty( rtn ) ? null : rtn;}/** * 构造properties文件 * @param path * @throws IOException*/public static Properties buildProperty(String path) throws IOException{InputStream is=getResourceAsStream("afei.properties");pro=new Properties();pro.load(is);return pro;}/** * 构造properties文件的流 * @param resource * @return */public static InputStream getResourceAsStream(String resource) {String stripped = resource.startsWith("/") ?resource.substring(1) : resource;InputStream stream = null;ClassLoader classLoader = Thread.currentThread().getContextClassLoader();if (classLoader!=null) {stream = classLoader.getResourceAsStream( stripped );}if ( stream == null ) {stream = TestMain.class.getResourceAsStream( resource );}if ( stream == null ) {stream = TestMain.class.getClassLoader().getResourceAsStream( stripped );}if ( stream == null ) {throw new RuntimeException( resource + " not found" );}return stream;}/** * 获得系统属性 当然 你可以选择从别的地方获取值 * @param systemPropertyName * @return */private static String extractFromSystem(String systemPropertyName) {try {return System.getProperty( systemPropertyName );}catch( Throwable t ) {return null;}}/** * 判断字符串的空(null或者.length=0) * @param string * @return */public static boolean isEmpty(String string) {return string == null || string.length() == 0;}}
afei.properties文件：
javaeye.url=www.iteye.comjavaeye.homepage=duyunfei.iteye.comjavaeye.username=${user.name}javaeye.password=123456home=${user.home}os=${os.name}userdir=${user.dir}javaversion=${java.version} javahome=${java.home}fileseparator=${file.separator}pathseparator=${path.separator}lineseparator=${line.separator}
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