如何對MySQL進行動態查詢

Question

我使用Spring MVC ，如何對Mysql進行動態查詢？ 我的控制器中有類似的內容： public String getNewsByDateAndAuthor(Model model, HttpServletRequest request) {}

如何將URL中的所有參數與request.getParameterMap() ，而我的地圖是<String, List<String>>來創建動態查詢呢？

例如，如果我有3個參數，我想生成一個查詢，如下所示：

SELECT * FROM news WHERE parameter = IN(val1, val2...) AND parameter2 = IN(val1, val2...) AND parameter3 = IN(val1, val2...)

或類似的東西，我只有一個參數；

SELECT * FROM news WHERE parameter = IN(val1, val2...)

如果有人知道，請告訴我我該怎么做。

我想要這樣的代碼：

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;
}

Answer 1

您不需要這樣的方法，也不想使用String concats創建動態查詢。 您要為此使用Criteria API 。

類似於以下內容

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();

由於有多個結果，您可能首先想創建一個Predicates列表，然后使用cq.where(cb.and(predicates.toArray(new Predicate[predicates.size()]);應用它們。

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();