java - 在java程序中加载属性

Question

我是一名初级java程序员；现在我正在使用 J2SE 和 NetBeans 6.9.1 来编写应用程序代码。

我现在面临的问题是使用单例类从本地文件系统中的众所周知的位置加载属性。令我恼火的是，我收到一个错误，该错误声称存在 throws 子句或捕获正在初始化 INSTANCE 变量的异常。希望有人能帮助我理解这一点。

提前致谢。

代码如下:

package cat.oai.atapplications.phot;

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

/**
 *
 * @author fdalmau
 */
public class PhotPropertiesManager {

    private static Properties photProperties;

    private PhotPropertiesManager() throws FileNotFoundException, IOException {
        photProperties = LoadProperties();
    }

    public static PhotPropertiesManager getInstance() {
        return PhotPropertiesManagerHolder.INSTANCE;
    }

    public static Properties getPhotProperties() {
        return PhotPropertiesManager.photProperties;
    }

    private static Properties LoadProperties() throws FileNotFoundException,
                                                      IOException {

        Properties defaultPhotProperties = new Properties();

        FileInputStream in = new FileInputStream("defaultphot");
        defaultPhotProperties.load(in);
        in.close();

        Properties applicationPhotProperties = 
                                     new Properties(defaultPhotProperties);

        in = new FileInputStream("lastexecutionphot");
        applicationPhotProperties.load(in);
        in.close();

        return applicationPhotProperties;
    }

    private static class PhotPropertiesManagerHolder {

        /******
          The problem is is this line of code:
         ******/
        static final PhotPropertiesManager INSTANCE = new PhotPropertiesManager();

    }
}

Answer 1

问题是静态字段不能抛出检查异常。我会像这样简化代码。

public enum PhotPropertiesManager {;
    private static final Properties PHOT_PROPERTIES = new Properties();

    static {
        try {
            load("defaultphot");
            load("lastexecutionphot");
        } catch (IOException e) {
            throw new IllegalStateException(e);
        }
    }

    private static void load(String filename) throws IOException {
        FileInputStream in = new FileInputStream(filename);
        PHOT_PROPERTIES.load(in);
        in.close();
    }

    public static Properties getPhotProperties() {
        return PHOT_PROPERTIES;
    }
}