fetch spec

EntityResource.java

@And({@Spec(path = "field1", spec = In.class),
  @Spec(path = "field2", spec = In.class),
  @Spec(path = "fetch", spec = FetchSpecification.class, constVal = {"lazyRelationship1", "lazyRelationship2"})}) 
  Specification<Entity> entitySpec,

FetchSpecification.java

/**
 * Copyright 2014-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.inteloom.jed.web.rest.util;

import javax.persistence.criteria.*;

import net.kaczmarzyk.spring.data.jpa.domain.PathSpecification;

import java.util.Arrays;
import java.util.List;

/**
 * <p>Extension to specification-arg-resolver to allow fetching in a specification
 *
 * @author Tomasz Kaczmarzyk
 * @author Gerald Humphries
 */
public class FetchSpecification<T> extends PathSpecification<T> {

    private List<String> expectedValues;

    public FetchSpecification(String path, String[] httpParamValues) {
        this(path, httpParamValues, null);
    }

    public FetchSpecification(String path, String[] httpParamValues, String[] config) {
        super(path);
        if (httpParamValues == null || httpParamValues.length < 1) {
            throw new IllegalArgumentException();
        }
        expectedValues = Arrays.asList(httpParamValues);
    }

    @Override
    public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
        if (Long.class != query.getResultType()) { // do not join in count queries
            for (String value : expectedValues){
                root.fetch(value, JoinType.LEFT);
            }
        }
        return null;
    }

}