[英]How to make a dynamic query for MySQL
我使用Spring MVC ,如何对Mysql进行动态查询? 我的控制器中有类似的内容: public String getNewsByDateAndAuthor(Model model, HttpServletRequest request) {}
如何将URL中的所有参数与request.getParameterMap()
,而我的地图是<String, List<String>>
来创建动态查询呢?
例如,如果我有3个参数,我想生成一个查询,如下所示:
SELECT * FROM news WHERE parameter = IN(val1, val2...) AND parameter2 = IN(val1, val2...) AND parameter3 = IN(val1, val2...)
或类似的东西,我只有一个参数;
SELECT * FROM news WHERE parameter = IN(val1, val2...)
如果有人知道,请告诉我我该怎么做。
我想要这样的代码:
public String getQuery(Map<String,List<String>> parameters){
List<String> author = new ArrayList<>();
List<String> startDate = new ArrayList<>();
List<String> endDate = new ArrayList<>();
List<String> categories = new ArrayList<>();
List<String> about = new ArrayList<>();
List<String> soureID = new ArrayList<>();
if (!parameters.get("author").isEmpty())
for (int i = 0; i < parameters.get("author").size(); i++) {
author.add(parameters.get("author").get(i));
}
if (!parameters.get("startDate").isEmpty())
for (int i = 0; i < parameters.get("startDate").size(); i++) {
startDate.add(parameters.get("startDate").get(i));
}
if (!parameters.get("endDate").isEmpty())
for (int i = 0; i < parameters.get("endDate").size(); i++) {
endDate.add(parameters.get("endDate").get(i));
}
if (!parameters.get("categories").isEmpty())
for (int i = 0; i < parameters.get("categories").size(); i++) {
categories.add(parameters.get("categories").get(i));
}
if (!parameters.get("about").isEmpty())
for (int i = 0; i < parameters.get("about").size(); i++) {
about.add(parameters.get("about").get(i));
}
if (!parameters.get("soureID").isEmpty())
for (int i = 0; i < parameters.get("soureID").size(); i++) {
soureID.add(parameters.get("soureID").get(i));
}
StringBuilder queryBuilder = new StringBuilder();
queryBuilder.append("SELECT * FROM news WHERE");
if (!author.isEmpty()) {
String authors = author.toString();
authors.replace(" ", " , ");
queryBuilder.append(" author = IN ( " + authors + " ) AND");
}
if (!startDate.isEmpty()) {
String startDates = startDate.toString();
startDates.replace(" ", " , ");
queryBuilder.append(" author = IN ( " + startDates + " ) AND");
}
if (!endDate.isEmpty()) {
String endDates = endDate.toString();
endDates.replace(" ", " , ");
queryBuilder.append(" author = IN ( " + endDates + " ) AND");
}
if (!categories.isEmpty()) {
String categoriesR = categories.toString();
categoriesR.replace(" ", " , ");
queryBuilder.append(" author = IN ( " + categoriesR + " ) AND");
}
if (!about.isEmpty()) {
String abouts = about.toString();
abouts.replace(" ", " , ");
queryBuilder.append(" author = IN ( " + abouts + " ) AND");
}
if (!soureID.isEmpty()) {
String sourceIDs = soureID.toString();
sourceIDs.replace(" ", " , ");
queryBuilder.append(" author = IN ( " + sourceIDs + " ) AND");
}
queryBuilder.delete(queryBuilder.length() - 3, queryBuilder.length());
String query = queryBuilder.toString();
return query;
}
您不需要这样的方法,也不想使用String concats创建动态查询。 您要为此使用Criteria
API 。
类似于以下内容
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<News> cq = cb.createQuery(News.class);
Root<News> news = cq.from(News.class);
if (!parameters.get("author").isEmpty()) {
cq.where(cb.in(news.get("author"), parameters.get("author"));
}
TypedQuery<News> query = em.createQuery(cq);
return query.getResultList();
由于有多个结果,您可能首先想创建一个Predicates
列表,然后使用cq.where(cb.and(predicates.toArray(new Predicate[predicates.size()]);
应用它们。
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<News> cq = cb.createQuery(News.class);
Root<News> news = cq.from(News.class);
List<Predicate> predicates = new ArrayList<Predicate>();
if (!parameters.get("author").isEmpty()) {
predicates.add(cb.in(news.get("author"), parameters.get("author")));
}
// Other params here.
cq.where(cb.and(predicates.toArray(new Predicate[predicates.size()]));
TypedQuery<News> query = em.createQuery(cq);
return query.getResultList();
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