Configuration

Java 中有個好用的物件, Properties, 可以將常常會修改的資料存在這裡 (file) , 通常會以 .properties 結尾, 也可以用 xml 檔案.

每次要使用時, 必須寫一堆 code :

package hank.jakarta.common.configuration;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Properties;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class ConfigurationTest {

    public static final Log log = LogFactory.getLog(ConfigurationTest.class);
    public static final String propName = "mmmm.properties";
    
    private String name;
    private String working;
    
    private Properties prop;
    
    private ConfigurationTest() {
        // do something
        try {
            initProp();
        } catch (IOException e) {
            log.error(e.getMessage(), e);
        }
    }

    private static class SingletonHolder {
        private static final ConfigurationTest instance = new ConfigurationTest();
    }

    public static ConfigurationTest getInstance() {
        return SingletonHolder.instance;
    }
    
    private void initProp() throws IOException {
        if (prop == null) {
            prop = new Properties();
            String realPath = getClass().getClassLoader().getResource(propName)
                    .getPath();
            File f = new File(realPath);
            if (!f.isFile()) {
                throw new FileNotFoundException("path not found!! : " + realPath);
            } else {
                prop.load(new FileInputStream(f));
                // load properties ......
                setName(prop.getProperty("name"));
                setWorking(prop.getProperty("working"));
            }
        }
    }
    
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getWorking() {
        return working;
    }

    public void setWorking(String working) {
        this.working = working;
    }

    public static void main(String[] args) {
        // test
        ConfigurationTest config = ConfigurationTest.getInstance();
        System.out.println(config.getName());
        System.out.println(config.getWorking());
    }
}

來看看紅色的地方, 每當使用時 (假設檔案是放在 classes 裡), 必須自己經過一些處理後, 再把變數都 setter 好, 才能使用. 這種是一般最常件的方法.

昨天在 surfing jakarta website 時, 看到一個好用的 tool - Jakarta commons-configuration
把一堆 code 都封裝了起來, 我們要用使就變得特別方便, 也可以設定他動態 reload 的方式.

package hank.jakarta.common.configuration;


import org.apache.commons.configuration.ConfigurationException;
import org.apache.commons.configuration.PropertiesConfiguration;
import org.apache.commons.configuration.reloading.FileChangedReloadingStrategy;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class ConfigurationTest1 {

    public static final Log log = LogFactory.getLog(ConfigurationTest1.class);
    public static final String propName = "mmmm.properties";
    
    private String name;
    private String working;
    
    private PropertiesConfiguration prop;
    
    private ConfigurationTest1() {
        // do something
        try {
            initProp();
        } catch (ConfigurationException e) {
            log.error(e.getMessage(), e);
        }
    }

    private static class SingletonHolder {
        private static final ConfigurationTest1 instance = new ConfigurationTest1();
    }

    public static ConfigurationTest1 getInstance() {
        return SingletonHolder.instance;
    }
    
    private void initProp() throws ConfigurationException {
        if (prop == null) {
            prop = new PropertiesConfiguration(propName);
        }
        // load properties ......
        // String
        setName(prop.getString("name"));
        setWorking(prop.getString("working"));
        // 如果是 double, 可以這樣寫, 就會幫你轉好了. 
        // prop.getDouble("double");
        
        // 其它像 integer, ...都是.
        
        // 那如何動態 reload 呢?, 其實很簡單
        prop.setReloadingStrategy(new FileChangedReloadingStrategy());
        
        // FileChangedReloadingStrategy <-- 這個是指, 當你修改了 attribute 時, 下一次去存取時, 會先去檢查最後修改日期, 來判斷他是否有修改, 如果有, 就 reaload.        

    }
    
    
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getWorking() {
        return working;
    }

    public void setWorking(String working) {
        this.working = working;
    }

    public static void main(String[] args) {
        ConfigurationTest1 config = ConfigurationTest1.getInstance();
        System.out.println(config.getName());
        System.out.println(config.getWorking());
    }
}

今天先分享到這. 打球囉.