在使用MyBatis-Plus進(jìn)行數(shù)據(jù)庫查詢時(shí)，構(gòu)建查詢條件是一項(xiàng)常見但重要的任務(wù)圈膏。本文將介紹如何通過優(yōu)化代碼來生成更高效和簡潔的查詢條件倔矾，以提高代碼質(zhì)量和開發(fā)效率驼抹。
背景
在許多Java應(yīng)用程序中浮还，我們使用MyBatis-Plus框架來處理數(shù)據(jù)庫查詢竟坛。通常，我們需要構(gòu)建查詢條件碑定，并使用QueryWrapper對象來表示這些條件流码。下面是一種常見的方法，用于根據(jù)查詢對象和其字段的注解來生成查詢條件：
public QueryWrapper<T> queryWrapperHandler(Q q) {
try {
// 獲取查詢對象的類和字段
Class<? extends EntityQuery> qClass = q.getClass();
Field[] fields = qClass.getDeclaredFields();
QueryWrapper<T> queryWrapper = new QueryWrapper<>();
Map<String, Field[]> betweenFieldMap = new HashMap<>();
// 處理@SelectColumn
SelectColumn selectColumn = qClass.getAnnotation(SelectColumn.class);
if (selectColumn != null && selectColumn.value() != null && selectColumn.value().length > 0) {
// 轉(zhuǎn)換字段名為下劃線風(fēng)格并設(shè)置為選擇字段
String[] strings = selectColumn.value();
for (int i = 0; i < strings.length; i++) {
strings[i] = StrUtil.toUnderlineCase(strings[i]);
}
queryWrapper.select(strings);
}
// 處理排序字段
String sortColumn = "";
String sortOrder = "";
for (Field field : fields) {
field.setAccessible(true);
Object value = field.get(q);
// 判斷屬性是否存在值
if (Objects.isNull(value) || String.valueOf(value).equals("null") || value.equals("")) {
continue;
}
// 處理@QuerySort注解
QuerySort querySort = field.getDeclaredAnnotation(QuerySort.class);
String paramValue = (String) field.get(q);
sortColumn = paramValue.isEmpty() ? (querySort != null ? querySort.value() : "") : paramValue;
// 處理@QueryOrder注解
QueryOrder queryOrder = field.getDeclaredAnnotation(QueryOrder.class);
paramValue = (String) field.get(q);
sortOrder = paramValue.isEmpty() ? (queryOrder != null ? queryOrder.value() : "") : paramValue;
// 處理@Query注解
Query query = field.getDeclaredAnnotation(Query.class);
if (query == null) {
continue;
}
// 獲取列名
String columnName = StrUtil.isBlank(query.column()) ? StrUtil.toUnderlineCase(field.getName()) : query.column();
// 根據(jù)注解生成查詢條件
switch (query.expression()) {
case EQ:
queryWrapper.eq(columnName, value);
break;
case NE:
queryWrapper.ne(columnName, value);
break;
case LIKE:
queryWrapper.like(columnName, value);
break;
case GT:
queryWrapper.gt(columnName, value);
break;
case GE:
queryWrapper.ge(columnName, value);
break;
case LT:
queryWrapper.lt(columnName, value);
break;
case LE:
queryWrapper.le(columnName, value);
break;
case IN:
queryWrapper.in(columnName, value);
break;
case NOT_IN:
queryWrapper.notIn(columnName, value);
break;
case IS_NULL:
queryWrapper.isNull(columnName);
break;
case NOT_NULL:
queryWrapper.isNotNull(columnName);
break;
case BETWEEN:
// 處理BETWEEN注解
if (betweenFieldMap.containsKey(columnName)) {
Field[] f = betweenFieldMap.get(columnName);
Field[] tempList = new Field[2];
tempList[0] = f[0];
tempList[1] = field;
betweenFieldMap.put(columnName, tempList);
} else {
betweenFieldMap.put(columnName, new Field[]{field});
}
break;
}
}
// 處理BETWEEN注解
Set<String> keySet = betweenFieldMap.keySet();
for (String key : keySet) {
Field[] itemFieldList = betweenFieldMap.get(key);
if (itemFieldList.length != 2){
throw new IllegalArgumentException("查詢參數(shù)數(shù)量對應(yīng)異常");
}
Field field1 = itemFieldList[0];
Field field2 = itemFieldList[1];
Query query1 = field1.getDeclaredAnnotation(Query.class);
if (field1.get(q) instanceof Date) {
// 處理日期類型
if (query1.left()) {
queryWrapper.apply("date_format(" + key + ",'%y%m%d') >= date_format({0},'%y%m%d')", field1.get(q));
queryWrapper.apply("date_format(" + key + ",'%y%m%d') <= date_format({0},'%y%m%d')", field2.get(q));
} else {
queryWrapper.apply("date_format(" + key + ",'%y%m%d') <= date_format({0},'%y%m%d')", field1.get(q));
queryWrapper.apply("date_format(" + key + ",'%y%m%d') >= date_format({0},'%y%m%d')", field2.get(q));
}
} else {
// 處理非日期類型
if (query1.left()) {
queryWrapper.between(key, field1.get(q), field2.get(q));
} else {
queryWrapper.between(key, field2.get(q), field1.get(q));
}
}
}
// 處理排序字段
if (sortOrder.equalsIgnoreCase("desc")) {
queryWrapper.orderByDesc(StrUtil.isNotBlank(sortColumn), StrUtil.toUnderlineCase(sortColumn));
} else {
queryWrapper.orderByAsc(StrUtil.isNotBlank(sortColumn), StrUtil.toUnderlineCase(sortColumn));
}
return queryWrapper;
} catch (Exception e) {
e.printStackTrace();
throw a RuntimeException(e.getMessage());
}
}
結(jié)論
通過對MyBatis-Plus查詢條件生成方法的優(yōu)化延刘，我們可以生成更高效、可維護(hù)和易讀的代碼六敬。這有助于提高開發(fā)效率碘赖，并減少潛在的bug。
