属性文件中的Spring和Constants类

Question

@Autowired
Constants constants;//in every class that needs constant
//...
constants.getArticleLimit()

Constants.ARTICLES_LIMIT //static var version

package org.simpletest.utils

import org.apache.log4j.Logger;

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

public class Constants {

    private static final Logger LOG = Logger.getLogger(Constants.class);

    public static final int ARTICLES_LIMIT;

    public static final String PROPERTIES_LOCATION = "constants.properties";

    static {
        Properties p = new Properties();

        //default values
        int articlesLimit = 10;

        Class<?> clazz = Constants.class.getClass(); 

        ClassLoader cl = clazz.getClassLoader();

        //try to load from properties file
        try(final InputStream is = cl.getResourceAsStream(PROPERTIES_LOCATION)){

            p.load(is);

            articlesLimit= Integer.parseInt(p.getProperty("articleslimit"));

        } catch (IOException e) {
            LOG.debug(String.format("Unable to load {0} properties file. Getting constants by default values.",PROPERTIES_LOCATION),e);
        }

        ARTICLES_LIMIT = articlesLimit;
    }
}

Answer 1

经过一些测试，这就是问题所在：

System.out.println(Constants.class.getClass());

这将打印java.lang.class，而ClassLoader可能没有加载这些文件。这是因为someclass.class的类是java.lang.class。

移除getclass()，Classloader将不会为空。不需要clazz变量。这应该是您所需要做的一切：

ClassLoader cl = Constants.class.getClassLoader();