java - 如何从与 Java 中的某个表达式匹配的字符串中获取值？

Question

我正在开发一个表达式值读取器。在到处寻找这样的 API 但没有找到任何东西后，我决定创建自己的 API。我创建了一个名为 ExpressionMatcher 的类。它应该是这样工作的:

    private static final String TEMPLATE = "my name is {username} and i am {userage} years old";
private ExpressionMatcher expressionMatcher = new ExpressionMatcher(TEMPLATE);
  ...
  String matias = "my name is Matias and i am 25 years old";
  String fede = "my name is Federico and i am 23 years old";

    Map<String, String> variables = expressionMatcher.getValuesFromString(matias);

    assertEquals("Matias", variables.get("username"));

表达式匹配器的代码是这样的:

public class ExpressionMatcher {

List<String> variableNames = new ArrayList<String>();
private final Pattern expressionPattern;

public ExpressionMatcher(String template) {
    // Look for variable names in the string
    Pattern pattern = Pattern.compile("\\{(.*?)\\}");
    Matcher matcher = pattern.matcher(template);
    while(matcher.find()) {
        // Add variable names into a list
        variableNames.add(matcher.group(1));
    }
    // replace the variable names with a new regex that will match all incoming expressions and compile a pattern
    this.expressionPattern = Pattern.compile(matcher.replaceAll("(.*?)"));

}

public Map<String, String> getValuesFromString(String expression) {
    Matcher matcher = this.expressionPattern.matcher(expression);
    Map<String, String> variables = new HashMap<String, String>();
    if(!matcher.matches()) {
        return Collections.emptyMap();
    } else {
        int i = 0;
        while(matcher.find()) {

            variables.put(variables.get(i), matcher.group(1));
            i++;
        }
    }
    return variables;
}

到目前为止，我已经能够成功获取变量名称，但无法获取纯文本表达式的值。我怎样才能做到这一点？谢谢，

Answer 1

没关系，

经过更多测试后，我解决了这个问题。在 getValueFromString 方法中，我添加了以下代码:

    public Map<String, String> getValuesFromExpression(String expression) {
    Matcher matcher = this.expressionPattern.matcher(expression);
    Map<String, String> variables = new HashMap<String, String>();
    if(!matcher.matches()) {
        return Collections.emptyMap();
    } else {
        // Iterate over the groups
        for(int i = 0; i < matcher.groupCount(); i++) {
            variables.put(variableNames.get(i), matcher.group(i + 1));
        }
    }
    return variables;
}

我希望至少这对某人有帮助。