真正动态的 JPA CriteriaBuilder

Question

I need to create a "real" dynamic JPA CriteriaBuilder . I get an Map<String, String> with the statements. It looks like:

name : John
surname : Smith
email : email@email.de

...more pairs possible

Here is what i implement:

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<User> query = cb.createQuery(User.class);
Root<User> userRoot = query.from(User.class);
query.select(userRoot);

List<Predicate> predicates = new ArrayList<Predicate>();
Iterator<String> column = statements.keySet().iterator();
while (column.hasNext()) {

    // get the pairs
    String colIndex = column.next();
    String colValue = statements.get(colIndex);

    // create the statement
    Predicate pAnd = cb.conjunction();
    pAnd = cb.and(pAnd, cb.equal(userRoot.get(colIndex), colValue));
    predicates.add(pAnd);
}

// doesn't work, i don't know how many predicates i have -> can not address them
query.where(predicates.get(0), predicates.get(1), ...);

// doesn't work, because it is a list of predicates
query.where(predicates);

// doesn't work, because the actual predicate overwrites the old predicate
for (Predicate pre : predicates) {
     query.where(pre)
}

I tried to build a big Predicate , which contains all other predicates and add this to the query.where() , but again the predicates overwrites old values. Looks like there is no possibility to add a Predicate instead of change a Predicate :-(

The real project is even more complicated, because some pairs requires an equal and some other a like . And that is not even enough: There could a extra statement with or included like type : 1;4;7 . Here the value have to split up and create a statement like:

<rest of statement> AND (type = 1 OR type = 4 OR type = 7)

UPDATE and SOLUTION Got two lists, first List for AND works well. Second list contains OR statements like exspected:

final List<Predicate> andPredicates = new ArrayList<Predicate>();
final List<Predicate> orPredicates = new ArrayList<Predicate>();
for (final Entry<String, String> entry : statements.entrySet()) {
    final String colIndex = entry.getKey();
    final String colValue = entry.getValue();
    if (colIndex != null && colValue != null) {

        if (!colValue.contains(";")) {
            if (equals) {
                andPredicates.add(cb.equal(userRoot.get(colIndex), colValue));
            } else {
                andPredicates.add(cb.like(userRoot.<String> get(colIndex), "%" + colValue + "%"));
            }
        } else {
            String[] values = colValue.split(";");
            for (String value : values) {
                orPredicates.add(cb.or(cb.equal(userRoot.get(colIndex), value)));
            }
        }       
    }
}

// Here goes the magic to combine both lists
if (andPredicates.size() > 0 && orPredicates.size() == 0) {
    // no need to make new predicate, it is already a conjunction
    query.where(andPredicates.toArray(new Predicate[andPredicates.size()]));
} else if (andPredicates.size() == 0 && orPredicates.size() > 0) {
    // make a disjunction, this part is missing above
    Predicate p = cb.disjunction();
    p = cb.or(orPredicates.toArray(new Predicate[orPredicates.size()]));
    query.where(p);
} else {
    // both types of statements combined
    Predicate o = cb.and(andPredicates.toArray(new Predicate[andPredicates.size()]));
    Predicate p = cb.or(orPredicates.toArray(new Predicate[orPredicates.size()]));
    query.where(o, p);
}

query.where(predicates.toArray(new Predicate[predicates.size()]));
users = em.createQuery(query).getResultList();

Answer 1

You can pass an array of predicates to the CriteriaBuilder , deciding on equal or like as you go. For this, build a list and pack the contents of the list into an array in a single and statement. Like this:

final List<Predicate> predicates = new ArrayList<Predicate>();

for (final Entry<String, String> e : myPredicateMap.entrySet()) {

    final String key = e.getKey();
    final String value = e.getValue();

    if ((key != null) && (value != null)) {

        if (value.contains("%")) {
            predicates.add(criteriaBuilder.like(root.<String> get(key), value));
        } else {
            predicates.add(criteriaBuilder.equal(root.get(key), value));
        }
    }
}

query.where(criteriaBuilder.and(predicates.toArray(new Predicate[predicates.size()])));
query.select(count);

In case you need to distingiush between and and or , use two lists.

Answer 2

One option is to use the fact that method with variable number of arguments can take an array:

query.where(predicates.toArray(new Predicate[predicates.size()])); 

Alternatively, you can combine them into a single predicate (note that if you don't do it, you don't need to create a conjunction as in your example);:

Predicate where = cb.conjunction();
while (column.hasNext()) {
    ...
    where = cb.and(where, cb.equal(userRoot.get(colIndex), colValue));
}

query.where(where);

Answer 3

I have always been thinking that creation of solution like that is like reinventing the bicycle. Here https://github.com/sasa7812/jfbdemo is my solution. It was tested on EclipseLink and Hibernate (EclipseLink in production, we used it in several projects for simple cases). Sometimes you just need a quick solution to make a dataTable with sorting and filtering, nothing fancy. It is able to filter and sort on joined fields, and even on collections. Project contains demo on Primefaces showing the abilities of FilterCriteriaBuilder. In the heart of it you just need this:

 public List<T> loadFilterBuilder(int first, int pageSize, Map<String, Boolean> sorts, List<FieldFilter> argumentFilters, Class<? extends AbstractEntity> entityClass) {
    FilterCriteriaBuilder<T> fcb = new FilterCriteriaBuilder<>(getEntityManager(), (Class<T>) entityClass);
    fcb.addFilters(argumentFilters).addOrders(sorts);
    Query q = getEntityManager().createQuery(fcb.getQuery());
    q.setFirstResult(first);
    q.setMaxResults(pageSize);
    return q.getResultList();
}

to get the results from database.

I really need someone to tell me that it is usefull and is used somewhere to continue my work on this library.

Answer 4

您可以转换为 Predicate ... 如下

query.where( predicates.stream().toArray( Predicate[]::new ) );

Answer 5

对于 Predicate，您可以创建新的 ArrayList 将所有谓词添加到列表中，然后最后您可以创建一个谓词数组并将列表转换为谓词数组并直接将其分配给 criteriabuilder.where(new Pridicate[])