order

This paper mainly studies the dynamic query of jpa

javax.persistence.criteria

The following shows the implementation of spring side branch 4.

springside branch 4

SearchFilter

/*******************************************************************************
 * Copyright (c) 2005, 2014 springside.github.io
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 *******************************************************************************/
package org.springside.modules.persistence;

import java.util.Map;
import java.util.Map.Entry;

import org.apache.commons.lang3.StringUtils;

import com.google.common.collect.Maps;

public class SearchFilter {

	public enum Operator {
		EQ, LIKE, GT, LT, GTE, LTE
	}

	public String fieldName;
	public Object value;
	public Operator operator;

	public SearchFilter(String fieldName, Operator operator, Object value) {
		this.fieldName = fieldName;
		this.value = value;
		this.operator = operator;
	}

	/**
	 * searchParams The format of key in is operator? Fieldname
	 */
	public static Map<String, SearchFilter> parse(Map<String, Object> searchParams) {
		Map<String, SearchFilter> filters = Maps.newHashMap();

		for (Entry<String, Object> entry : searchParams.entrySet()) {
			// Filter out null values
			String key = entry.getKey();
			Object value = entry.getValue();
			if (StringUtils.isBlank((String) value)) {
				continue;
			}

			// Split operator and filedAttribute
			String[] names = StringUtils.split(key, "_");
			if (names.length != 2) {
				throw new IllegalArgumentException(key + " is not a valid search filter name");
			}
			String filedName = names[1];
			Operator operator = Operator.valueOf(names[0]);

			// Create searchFilter
			SearchFilter filter = new SearchFilter(filedName, operator, value);
			filters.put(key, filter);
		}

		return filters;
	}
}

DynamicSpecifications

/*******************************************************************************
 * Copyright (c) 2005, 2014 springside.github.io
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 *******************************************************************************/
package org.springside.modules.persistence;

import java.util.Collection;
import java.util.List;

import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Path;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

import org.apache.commons.lang3.StringUtils;
import org.springframework.data.jpa.domain.Specification;
import org.springside.modules.utils.Collections3;

import com.google.common.collect.Lists;

public class DynamicSpecifications {

	public static <T> Specification<T> bySearchFilter(final Collection<SearchFilter> filters, final Class<T> entityClazz) {
		return new Specification<T>() {
			@Override
			public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder builder) {
				if (Collections3.isNotEmpty(filters)) {

					List<Predicate> predicates = Lists.newArrayList();
					for (SearchFilter filter : filters) {
						// The nested path translate, such as the filedName named "user. Name" of the Task, is converted to the Task.user.name attribute
						String[] names = StringUtils.split(filter.fieldName, ".");
						Path expression = root.get(names[0]);
						for (int i = 1; i < names.length; i++) {
							expression = expression.get(names[i]);
						}

						// logic operator
						switch (filter.operator) {
						case EQ:
							predicates.add(builder.equal(expression, filter.value));
							break;
						case LIKE:
							predicates.add(builder.like(expression, "%" + filter.value + "%"));
							break;
						case GT:
							predicates.add(builder.greaterThan(expression, (Comparable) filter.value));
							break;
						case LT:
							predicates.add(builder.lessThan(expression, (Comparable) filter.value));
							break;
						case GTE:
							predicates.add(builder.greaterThanOrEqualTo(expression, (Comparable) filter.value));
							break;
						case LTE:
							predicates.add(builder.lessThanOrEqualTo(expression, (Comparable) filter.value));
							break;
						}
					}

					// Combine all conditions with and
					if (!predicates.isEmpty()) {
						return builder.and(predicates.toArray(new Predicate[predicates.size()]));
					}
				}

				return builder.conjunction();
			}
		};
	}
}

Summary

By using the dynamic specifications of springside and mapping the parameters of mvc to SearchFilter, you can also implement a set of end-to-end dynamic queries by yourself.

doc

• SearchFilter
• DynamicSpecifications
• Using RSQL to realize end-to-end dynamic query