爪哇 - 從字符串使用模板提取鍵值對

Question

所以有這個類org.apache.commons.lang3.text稱爲StrSubstitutor它可以在一張地圖這樣的：

Map<String, String> params = new HashMap<String, String>(); 
params.put("name","Vivek"); 
params.put("id","900"); 
params.put("somethingelse","blah"); 

和一個模板字符串是這樣的：

<data> 
     <id>${id}</id> 
     <name>${name}</name> 
     <something>${somethingelse}</something> 
    </data> 

產生一個輸出字符串是這樣的：

<data> 
     <id>900</id> 
     <name>Vivek</name> 
     <something>blah</something> 
    </data> 

我要的是相反的。有沒有一種方法可以讓輸出字符串和模板使用模板變量作爲鍵和字符串中相應的值作爲值來填充地圖？

PS - 我將使用的字符串不一定總是XML。這僅僅是一個例子。

編輯：我覺得有些困惑，變量名和標籤名稱是一樣的。標籤只是說明性的，與問題無關。這是我關心的$ {}中的變量。我添加了另一個標籤來顯示我的意思。

Answer 1

你可以用一個模式來格式字符串轉換成正則表達式，然後用這個表達式進步的輸入字符串，下面的示例類：

public final class FormatReader { 

    private final Pattern formatPattern; 
    private final List<String> names; 

    private FormatReader(
      final Pattern formatPattern, 
      final List<String> names) { 
     //// 
     this.formatPattern = formatPattern; 
     this.names = names; 
    } 

    public static FormatReader of(
      final String prefix, 
      final String suffix, 
      final String format) { 
     //// 
     return of(prefix, suffix, format, true); 
    } 

    public static FormatReader of(
      final String prefix, 
      final String suffix, 
      final String format, 
      final boolean allowSurroundingWhitespace) { 
     //// 
     // This method is somewhat ugly... 
     final List<String> names = new ArrayList<>(); 
     final StringBuilder sb = new StringBuilder("(?m)"); 
     boolean skip = allowSurroundingWhitespace; 
     if (skip) 
      sb.append("\\s*"); 
     for (int i = 0, last = 0, prefixLength = prefix.length(), suffixLength = suffix.length();;) { 
      if (i == format.length()) { 
       if (!skip) 
        sb.append(Pattern.quote(format.substring(last))); 
       break; 
      } 
      if (format.startsWith(prefix, i)) { 
       skip = true; 
       sb.append(Pattern.quote(format.substring(last, i))).append("(.+)"); 

       final int off = i + prefixLength; 
       names.add(format.substring(off, i = format.indexOf(suffix, off))); 
       i += suffixLength; 
       continue; 
      } 
      if (Character.isWhitespace(format.charAt(i))) { 
       if (!skip) { 
        skip = true; 
        // Replace '\s*' with '\s+' if at least one whitespace has to be present 
        sb.append(Pattern.quote(format.substring(last, i))).append("\\s*"); 
       } 
      } else if (skip) { 
       last = i; 
       skip = false; 
      } 
      i++; 
     } 
     if (!skip && allowSurroundingWhitespace) 
      sb.append("\\s*"); 
     return new FormatReader(Pattern.compile(sb.toString()), names); 
    } 

    public Map<String, String> toMap(
      final String input) { 
     //// 
     final Matcher m = formatPattern.matcher(input); 
     if (!m.matches()) 
      throw new IllegalArgumentException("Argument does not match format"); 
     final Map<String, String> map = new HashMap<>(); 
     for (int i = 0; i < m.groupCount();) 
      map.put(names.get(i), m.group(++i)); 
     return map; 
    } 

    public static void main(
      final String[] args) { 
     //// 
     final FormatReader r = of("${", "}", "" 
       + " <data>\n" 
       + "  <id>${id}</id>\n" 
       + "  <name>${name}</name>\n" 
       + " </data>"); 
     final String s = "" 
       + "  <data>\n" 
       + "  <id>900</id>   " 
       + " <name>Vivek</name>\n" 
       + " </data> "; 
     // The created pattern (accepts any count of whitespace): 
     //        'id'      'name' 
     // (?m)\s*\Q<data>\E\s*\Q<id>\E(.+)\Q</id>\E\s*\Q<name>\E(.+)\Q</name>\E\s*\Q</data>\E\s* 
     System.out.println(r.toMap(s)); // {name=Vivek, id=900} 
    } 
} 

Answer 2

這裏是另一種選擇：

import java.util.HashMap; 
import java.util.Map; 

public class Test{ 

    public static void main(String[] args){ 

     //simulate template. Assuming no more than on param in line 
     String[] template = new String[]{ 
            "<data>", 
            "<id>${id}</id>", 
            "<name>${name}</name>", 
            "<something>${somethingelse}</something>", 
            "</data>" 
            }; 

     String[] output = new String[]{ 
            "<data>", 
            "<id>900</id>", 
            "<name>Vivek</name>", 
            "<somethingelse>blah</somethingelse>", 
            "</data>" 
            }; 

     Map<String, String> params = getParams(template); 

     getValues(params, output); 

     for(String key : params.keySet()) { 
      System.out.println(key +" : " + params.get(key)); 
     } 
    } 

    private static Map<String, String> getParams(String[] template) { 

     Map<String, String> params = new HashMap<String, String>(); 

     for (String line : template) { 

      //get location of 3 chars ${} 
      int index$ = line.indexOf("$"); 
      int indexLeftB = line.indexOf("{"); 
      int indexRightB = line.indexOf("}"); 

      //make sure all ${} are present 
      if((index$ <0) || (indexLeftB <0) || (indexRightB <0)) { 
       continue; 
      } 

      //make sure they are in the right order 
      if(((indexLeftB - index$) !=1) || (indexRightB < indexLeftB)) { 
       continue; 
      } 

      //get param 
      String param = getParamFromLine(line, indexLeftB+1 , indexRightB); 

      if(param != null) { 

       params.put(param,null); 
      } 
     } 

     return params; 
    } 

    private static void getValues(Map<String, String> params, String[] output) { 

     //iterate over map 
     for(String param : params.keySet()) { 

      String tag = "<"+param+">"; //like <name> 
      String closeTag = "</"+param+">"; //like <name> 

      //iterate over output 
      for(String line : output) { 

       line = line.trim(); //remove all whitespace 
       //look for first occurrence of patternToSearch 
       int index1 = line.indexOf(tag, 0); 
       int index2 = line.indexOf(closeTag, index1); 

       //make sure there are 2 occurrences in 
       if((index1 < 0) || (index2 < 0)) { 
        continue; 
       } 

       String value = getParamFromLine(line, index1+ tag.length(), index2); 
       if(value != null) { 

        params.put(param, value); 
       } 
      } 
     } 
    } 

    private static String getParamFromLine(String line, int indexLeftB, int indexRightB) { 

     String param = line.substring(indexLeftB, indexRightB); 

     return (param.trim().length() == 0) ? null : param.trim(); 
    } 
}