如果存在命令行值,则覆盖属性文件

Question

我有一个程序,config.properties如果命令行除config.properties文件位置之外不包含任何参数,它将从文件中读取所有内容.下面是我的config.properties文件 -

NUMBER_OF_THREADS: 100
NUMBER_OF_TASKS: 10000
ID_START_RANGE: 1
TABLES: TABLE1,TABLE2

如果我从命令提示符运行我的程序,就像这样 -

java -jar Test.jar "C:\\test\\config.properties"

它应该读取config.properties文件中的所有四个属性.但是假设我运行的程序是这样的 -

java -jar Test.jar "C:\\test\\config.properties" 10 100 2 TABLE1 TABLE2 TABLE3

然后它应该从参数中读取所有属性并覆盖config.properties文件中的属性.

以下是我的代码,在这种情况下工作正常 -

public static void main(String[] args) {

        try {

            readPropertyFiles(args);

        } catch (Exception e) {
            LOG.error("Threw a Exception in" + CNAME + e);
        }
    }

    private static void readPropertyFiles(String[] args) throws FileNotFoundException, IOException {

        location = args[0];

        prop.load(new FileInputStream(location));

        if(args.length >= 1) {
            noOfThreads = Integer.parseInt(args[1]);
            noOfTasks = Integer.parseInt(args[2]);
            startRange = Integer.parseInt(args[3]);

            tableName = new String[args.length - 4];
            for (int i = 0; i < tableName.length; i++) {
                tableName[i] = args[i + 4];
                tableNames.add(tableName[i]);
            }
        } else {
            noOfThreads = Integer.parseInt(prop.getProperty("NUMBER_OF_THREADS").trim());
            noOfTasks = Integer.parseInt(prop.getProperty("NUMBER_OF_TASKS").trim());
            startRange = Integer.parseInt(prop.getProperty("ID_START_RANGE").trim());
            tableNames = Arrays.asList(prop.getProperty("TABLES").trim().split(","));
        }

        for (String arg : tableNames) {

            //Some Other Code

        }
    }   

问题陈述:-

现在我要做的是 - 假设任何人正在运行这样的程序

java -jar Test.jar "C:\\test\\config.properties" 10

然后在我的程序,它应该覆盖noOfThreadsonly-

noOfThreads should be 10 instead of 100

假设那个人正在运行这样的程序 -

java -jar Test.jar "C:\\test\\config.properties" 10 100

然后在我的程序,它应该覆盖noOfThreads和noOfTasksonly-

noOfThreads should be 10 instead of 100
noOfTasks should be 100 instead of 10000

还有其他可能的用例.

任何人都可以建议我如何实现这种情况？谢谢您的帮助

Answer 1

定义命令行输入时如下

java -jar Test.jar "C:\\test\\config.properties" 10 100

这意味着必须始终提供noOfThreads覆盖noOfTasks.

要解决此问题,您可以在命令行上将这些指定为系统属性以及文件位置,其他方面也具有默认位置.例如: -

java -jar -Dconfig.file.location="C:\\test\\config.properties" -DNUMBER_OF_THREADS=10 Test.jar

然后.

1. 将文件属性读入Properties.
2. 迭代属性中的键并找到相应的System.getProperty().
3. 如果找到值,则覆盖属性中的相应条目.

这样,无论您引入多少新属性,您的代码都将保持不变.

你可以走得更远一步,封装了所有的这一场PropertyUtil还提供了实用的方法,如getIntProperty(),getStringProperty()等.

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

public class PropertyUtil {

  private static final String DEFAULT_CONFIG_FILE_LOCATION = "config.properties";

  private String configFileLocation;

  private Properties properties;

  public PropertyUtil() throws IOException {

    this(DEFAULT_CONFIG_FILE_LOCATION);
  }

  public PropertyUtil(String configFileLocation) throws IOException {

    this.configFileLocation = configFileLocation;
    this.properties = new Properties();
    init();
  }

  private void init() throws IOException {

    properties.load(new FileInputStream(this.configFileLocation));

    for (Object key : this.properties.keySet()) {

      String override = System.getProperty((String) key);

      if (override != null) {

        properties.put(key, override);
      }
    }
  }

  public int getIntProperty(String key) {

    return this.properties.contains(key) ? Integer.parseInt(properties.get(key)) : null;
  }

  public String getStringProperty(String key) {

    return (String) this.properties.get(key);
  }
}

例子.

config.properties

NUMBER_OF_THREADS=100
NUMBER_OF_TASKS=10000
ID_START_RANGE=1
TABLES=TABLE1,TABLE2

要覆盖NUMBER_OF_THREADS.

java -jar -Dconfig.file.location="C:\\test\\config.properties" -DNUMBER_OF_THREADS=10 Test.jar

将'NUMBER_OF_THREADS'作为int读取的简短示例.

new PropertyUtil(System.getProperty("config.file.location")).getIntProperty("NUMBER_OF_THREADS");

Answer 2

相反，创建一个循环。

List<String> paramNames = new ArrayList<String>{"NUMBER_OF_THREADS", "NUMBER_OF_TASKS", 
            "ID_START_RANGE", "TABLES"}; // Try to reuse the names from the property file
Map<String, String> paramMap = new HashMap<String, String>();
...
// Validate the length of args here
...
// As you table names can be passed separately. You need to handle that somehow. 
// This implementation would work when number of args will be equal to number of param names
for(int i = 0; i< args.length; i++) {
   paramMap.put(paramNames[i], args[i]); 
}

props.putAll(paramMap);
... // Here props should have it's values overridden with the ones provided