【Java代码之美】 -- Java使用表驱动的方式处理if..else过多的问题

业务背景：

最近有同事在做门禁未生效预警系统。审核提交的代码时，发现了一段熟悉的内容，内容如下。

这段代码看着很眼熟，查阅了一下，发现之前悦荟在之前优化其它服务的时候优化过这段代码，暂时就不追究为什么这段代码竟然存在于多个服务中了，还是尽早改掉就好。通过阅读代码，发现按照上次的经验，从根源处ThresholdInfoData的结构进行重新设计优化，可能不好修改，设计的地方会比较多。于是考虑采用一种简洁快速的方式，先优化掉这种if else过多的情况——表驱动的方式。

修改前代码：

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private void setThresholdValue(ThresholdInfoData thresholdInfoData, net.sf.json.JSONArray thresholds) {     if (thresholds.isEmpty()) {         logger.info("thresholds is null");         return;     }      int thresSize = thresholds.size();     for (int j = 0; j < thresSize; j++) {         if (thresholds.getJSONObject(j).has(Constant.VALUE)) {             String threshold_desc = thresholds.getJSONObject(j).getString(Constant.THRESHOLD_DESC);             double value = Double.parseDouble(thresholds.getJSONObject(j).getString(Constant.VALUE));             int validityValue = Constant.ZERO;             validityValue = thresholds.getJSONObject(j).get("validity") == null ? validityValue : thresholds.getJSONObject(j).getInt("validity");             value = validityValue == 1 ? Constant.TEN_THOUSAND : value;             if (threshold_desc.equals(Constant.OPENINGRATE)) {                 thresholdInfoData.setOpeningRate(value);             } else if (threshold_desc.equals(Constant.COMPLE_TOTAL_ERROR_THRESHOLD)) {                 thresholdInfoData.setCompileError(value);                 thresholdInfoData.setCompileValidity(validityValue);             } else if (threshold_desc.equals(Constant.CMTRICS_UNSAFE_FUNC_THRESHOLD)) {                    thresholdInfoData.setCscheckerUnsafe(value);                    thresholdInfoData.setCscheckerUnsafeValidity(validityValue);             } else if (threshold_desc.equals(Constant.CMETRICS_REDUNDANT_CODE_TOATL_THRESHOLD)) {                  thresholdInfoData.setCscheckerIf0(value);                  thresholdInfoData.setCscheckerIf0Validity(validityValue);         } else if (threshold_desc.equals(Constant.STATIC_ERROR)) {                  thresholdInfoData.setStatiError(value);                  thresholdInfoData.setStatiErrorValidity(value);         } else if (threshold_desc.equals(Constant.SOURCEMONITOR_NEW_METHOD_COMPLEXITY_THRESHOLD)) {                  thresholdInfoData.setSourcemonitorComplexity(value);         } else if (threshold_desc.equals(Constant.SOURCEMONITOR_NEW_METHOD_STATEMENT_THRESHOLD)) {                 thresholdInfoData.setSourcemonitorStatement(value);         } else if (threshold_desc.equals(Constant.CMETRICS_CODE_DUPLICATION_RATIO_THRESHOLD)) {                 thresholdInfoData.setSimianDuplicationpercent(value);                 thresholdInfoData.setSimianDuplicationpercentValidity(validityValue);         } else if (threshold_desc.equals(Constant.CMETRICS_FILE_DUPLICATION_RATIO_THRESHOLD)) {                 thresholdInfoData.setMetricRepeatFilesRate(value);                 thresholdInfoData.setMetricRepeatFilesRateValidity(validityValue);         } else if (threshold_desc.equals(Constant.LLT_TC_CHANGED_COVERAGE_THRESHOLD)) {              thresholdInfoData.setLltChangedCoverage(value);         } else if (threshold_desc.equals(Constant.LLT_TC_PASS_PERCENT_THRESHOLD)) {             thresholdInfoData.setLltPassPercent(value);         }         }     } }

修改后的代码：

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private void setThresholdValue(ThresholdInfoData thresholdInfoData, net.sf.json.JSONArray thresholds) {         if (thresholds.isEmpty()) {                 logger.info("thresholds is null");                 return;         }         int thresSize = thresholds.size();         for (int j = 0; j < thresSize; j++) {             if (thresholds.getJSONObject(j).has(Constant.VALUE)) {                 String threshold_desc = thresholds.getJSONObject(j).getString(Constant.THRESHOLD_DESC);                 double value = Double.parseDouble(thresholds.getJSONObject(j).getString(Constant.VALUE));                  int validityValue = Constant.ZERO;                  validityValue = thresholds.getJSONObject(j).get("validity") == null ? validityValue : thresholds.getJSONObject(j).getInt("validity");                  value = validityValue == 1 ? Constant.TEN_THOUSAND : value;                  Map<String, BiConSumer<Double, Integer>> actionMappings = getComparisionTable(thresholdInfoData);                  try {                         actionMappings.get(threshold_desc).accept(value, validityValue);                 } catch (NullPointerException e) {                         logger.warn("get" + threshold_desc + " is null");                 }             }         } }     // 生成阈值描述和不同赋值方法的对照表 private Map<String, BiConsumer<Double, Integer>> getComparisionTable(ThresholdInfoData thresholdInfoData) {     Map<String, BiConsumer<Double, Integer>> actionMappings = new HashMap<>();     actionMappings.put(Constant.OPENNINGRATE, (a, b) -> {thresholdInfoData.setOpeningRate(a);});  actionMappings.put(Constant.COMPILE_TOTAL_ERROR_THRESHOLD, (a, b) -> {     thresholdInfoData.setCompileError(a);     thresholdInfoData.setCompileValidity(b);  });   actionMappings.put(Constant.CSCHECKER_UNSAFE_FUNC_THRESHOLD, (a, b) -> {     thresholdInfoData.setCscheckUnsafe(a);     thresholdInfoData.setCscheckerUnsafeValidity(b);  }); actionMappings.put(Constant.CMTRICS_REDUNDANT_CODE_TOATL_THRESHOLD, (a, b) -> {     thresholdInfoData.setCscheckerIf0(a);     thresholdInfoData.setCscheckerIf0Validity(b);  }); actionMappings.put(Constant.STATIC_ERROR, (a, b) -> {     thresholdInfoData.setStatiError(a);     thresholdInfoData.setStatuErrorValidity(b);  }); actionMappings.put(Constant.SOURCEMONITOR_NEW_METHOD_COMPLEXITY_THRESHOLD, (a, b) -> {     thresholdInfoData.setSourcemonitorComplexity(a);  }); actionMappings.put(Constant.SOURCEMONITOR_NEW_METHOD_STATEMNET_THRESHOLD, (a, b) -> {     thresholdInfoData.setSourcemonitorStatement(a);  }); actionMappings.put(Constant.CMETRICS_CODE_DUPLICATION_RATIO_THRESHOLD, (a, b) -> {     thresholdInfoData.setSimianDuplicationpercent(a);     thresholdInfoData.setSimianDuplicationpercentValidity(b);  }); actionMappings.put(Constant.CMETRICS_FILE_DUPLICATION_RATIO_THRESHOLD, (a, b) -> {     thresholdInfoData.setMetricRepeatFilesRate(a);     thresholdInfoData.setMetricRepeatFilesRateValidity(b);  }); actionMappings.put(Constant.LLT_TC_CHANGED_COVERAGE_THRESHOLD, (a, b) -> {     thresholdInfoData.setLltChangedCoverage(a);  }); actionMappings.put(Constant.LLT_TC_PASS_PERCENT_THRESHOLD, (a, b) -> {     thresholdInfoData.setLltPassPercent(a);  });   return actionMappings; }

　　

总结：

对于上述这种逻辑表达模式固定的if else代码，适用表驱动的方式进行解决。即通过某种映射关系，将逻辑表达式用表格的方式表示；再使用表格查找的方式，找到某个输入所对应的处理函数，适用这个处理函数进行运算。除表驱动的方式，还可以考虑使用反射、策略模式+注解等多种方式处理。

当然，最好的方式还是在最初设计的时候，就做好充分的考虑和结构设计，从根源上避免产生这样的代码。