使用單例模式加載properties文件

@(JAVA)[java]

* 這里只是用于示范單例模式，更好的辦法是使用java.util.ResourceBundle解釋proerties文件。詳見java.util.ResourceBundle的介紹文章 *

先準(zhǔn)備測試程序

package org.jediael.util; import static org.junit.Assert.*; import org.junit.Test;public class BasicConfigurationTest {@Testpublic void testGetValue(){BasicConfiguration configuration = BasicConfiguration.getInstance();assertTrue(configuration.getValue("key").equals("value"));} }

其中properties文件中有一行如下：

key=value

優(yōu)先選擇方案三

方式一：懶漢方式

到第一次使用實(shí)例時(shí)，才加載實(shí)例

package org.jediael.util;import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.util.Properties;public class BasicConfiguration {private static BasicConfiguration configuration = null;private Properties pros = null;public static synchronized BasicConfiguration getInstance(){if(configuration == null){configuration = new BasicConfiguration();}return configuration;}public String getValue(String key){return pros.getProperty(key);}private BasicConfiguration(){readConfig();}private void readConfig() {pros = new Properties();InputStream in = null;try {in = new FileInputStream(Thread.currentThread().getContextClassLoader().getResource("").getPath() + "search.properties");pros.load(in);} catch (FileNotFoundException e) {e.printStackTrace();}catch (IOException e) {e.printStackTrace();}finally{try {in.close();} catch (IOException e) {e.printStackTrace();}}} }

上述程序中，產(chǎn)生了BasicConfiguration的一個單例。

好處是只有到第一次調(diào)用getInstance才生成對象，節(jié)省了空間。不足之處在于同步鎖導(dǎo)致有可能執(zhí)行過慢。

2、餓漢方式

package org.jediael.util;import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.util.Properties;public class BasicConfiguration {private static BasicConfiguration configuration = new BasicConfiguration();private Properties pros = null;public static BasicConfiguration getInstance(){return configuration;}public String getValue(String key){return pros.getProperty(key);}private BasicConfiguration(){readConfig();}private void readConfig() {pros = new Properties();InputStream in = null;try {in = new FileInputStream(Thread.currentThread().getContextClassLoader().getResource("").getPath() + "search.properties");pros.load(in);} catch (FileNotFoundException e) {e.printStackTrace();}catch (IOException e) {e.printStackTrace();}finally{try {in.close();} catch (IOException e) {e.printStackTrace();}}} }

由于BasicConfiguration的實(shí)例是static，因此，當(dāng)類被加載時(shí)就會初始化，但這樣即使并不需要使用此實(shí)例，也會被初始化，導(dǎo)致內(nèi)存空間的浪費(fèi)。

方式三：內(nèi)部類方式

由于初始化放在內(nèi)部類中，只有當(dāng)此內(nèi)部類被使用時(shí)，才會進(jìn)行初始化。從而既節(jié)省了空間，也無需同步代碼。

package org.jediael.util;import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.util.Properties;public class BasicConfiguration {private Properties pros = null;private static class ConfigurationHolder{private static BasicConfiguration configuration = new BasicConfiguration();}public static BasicConfiguration getInstance(){return ConfigurationHolder.configuration;}public String getValue(String key){return pros.getProperty(key);}private BasicConfiguration(){readConfig();}private void readConfig() {pros = new Properties();InputStream in = null;try {in = new FileInputStream(Thread.currentThread().getContextClassLoader().getResource("").getPath() + "search.properties");pros.load(in);} catch (FileNotFoundException e) {e.printStackTrace();}catch (IOException e) {e.printStackTrace();}finally{try {in.close();} catch (IOException e) {e.printStackTrace();}}} }

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