java是否用实际值替换环境变量占位符？

Question

在我的申请中。属性文件我使用的是这样的键和值

report.custom.templates.path=${CATALINA_HOME}\\\\Medic\\\\src\\\\main\\\\reports\\\\AllReports\\\\

我需要用实际路径替换${CATALINA_HOME}：

{CATALINA_HOME} = C:\Users\s57893\softwares\apache-tomcat-7.0.27

这是我的代码：

public class ReadEnvironmentVar {  

 public static void main(String args[]) {

    String path = getConfigBundle().getString("report.custom.templates.path");
    System.out.println("Application Resources : " + path);
    String actualPath = resolveEnvVars(path);
    System.out.println("Actual Path : " + actualPath);

   }

private static ResourceBundle getConfigBundle() {
    return ResourceBundle.getBundle("medicweb");
 }

private static String resolveEnvVars(String input) {
    if (null == input) {
        return null;
     }

    Pattern p = Pattern.compile("\\$\\{(\\w+)\\}|\\$(\\w+)");
    Matcher m = p.matcher(input);
    StringBuffer sb = new StringBuffer();
    while (m.find()) {
        String envVarName = null == m.group(1) ? m.group(2) : m.group(1);
        String envVarValue = System.getenv(envVarName);
        m.appendReplacement(sb, null == envVarValue ? "" : envVarValue);
     }
    m.appendTail(sb);
    return sb.toString();
  }
}

从我的代码中，我得到的结果是-

实际路径：

 C:Userss57893softwaresapache-tomcat-7.0.27\Medic\src\main\reports\AllReports\

但我需要结果-

实际路径：

C:\Users\s57893\softwares\apache-tomcat-7.0.27\Medic\src\main\reports\AllReports\

请给我举个例子

Answer 1

由于appendReplacement()的工作方式，您需要避开环境变量中的反斜杠。从the Javadocs

Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string. Dollar signs may be treated as references to captured subsequences as described above, and backslashes are used to escape literal characters in the replacement string.

我会使用：

m.appendReplacement(sb, 
    null == envVarValue ? "" : Matcher.quoteReplacement(envVarValue));