Generic querydsl orderBy dynamic path generation with left joins

Question

I\'ve run into a problem while using JPA with Querydsl and Hibernate for data storage management. The sample model is as follows:

@Entity
public class User {         


        

Answer 1

I added now a protoype of the implementation to the test side of Querydsl https://github.com/mysema/querydsl/issues/582

I will consider a direct integration into Querydsl if this a common use case

public class OrderHelper {

private static final Pattern DOT = Pattern.compile("\\.");

public static PathBuilder<?> join(JPACommonQuery<?> query, PathBuilder<?> builder, Map<String, PathBuilder<?>> joins, String path) {
    PathBuilder<?> rv = joins.get(path);
    if (rv == null) {
        if (path.contains(".")) {
            String[] tokens = DOT.split(path);
            String[] parent = new String[tokens.length - 1];
            System.arraycopy(tokens, 0, parent, 0, tokens.length - 1);
            String parentKey = StringUtils.join(parent, ".");
            builder = join(query, builder, joins, parentKey);
            rv = new PathBuilder(Object.class, StringUtils.join(tokens, "_"));
            query.leftJoin((EntityPath)builder.get(tokens[tokens.length - 1]), rv);
        } else {
            rv = new PathBuilder(Object.class, path);
            query.leftJoin((EntityPath)builder.get(path), rv);
        }
        joins.put(path, rv);
    }
    return rv;
}

public static void orderBy(JPACommonQuery<?> query, EntityPath<?> entity, List<String> order) {
    PathBuilder<?> builder = new PathBuilder(entity.getType(), entity.getMetadata());
    Map<String, PathBuilder<?>> joins = Maps.newHashMap();

    for (String entry : order) {
        String[] tokens = DOT.split(entry);
        if (tokens.length > 1) {
            String[] parent = new String[tokens.length - 1];
            System.arraycopy(tokens, 0, parent, 0, tokens.length - 1);
            PathBuilder<?> parentAlias = join(query, builder, joins, StringUtils.join(parent, "."));
            query.orderBy(parentAlias.getString(tokens[tokens.length - 1]).asc());
        } else {
            query.orderBy(builder.getString(tokens[0]).asc());
        }
    }
}

}