springdata jpa封装数据库关键字（EQ, LIKE, GT, LT, GTE, LTE,IN）

数据库关键字申明，类SearchFilter：

/*******************************************************************************
 * Copyright (c) 2005, 2014 springside.github.io
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 *******************************************************************************/
package com.clearpro.common.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,IN
	}

	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中key的格式为OPERATOR_FIELDNAME
	 */
	public static Map parse(Map searchParams) {
		Map filters = Maps.newHashMap();

		for (Entry entry : searchParams.entrySet()) {
			// 过滤掉空值
			String key = entry.getKey();
			Object value = entry.getValue();
			/*if (StringUtils.isBlank((String) value)) {
				continue;
			}*/

			// 拆分operator与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]);

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

		return filters;
	}
}

关键字匹配的sql处理，类DynamicSpecifications：

/*******************************************************************************
 * Copyright (c) 2005, 2014 springside.github.io
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 *******************************************************************************/
package com.clearpro.common.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 com.clearpro.common.modules.utils.Collections3;
import com.google.common.collect.Lists;

public class DynamicSpecifications {

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

					List predicates = Lists.newArrayList();
					for (SearchFilter filter : filters) {
						// nested path translate, 如Task的名为"user.name"的filedName, 转换为Task.user.name属性
						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;
						case IN:
							predicates.add(expression.in(filter.value));
							break;
						}
					}

					// 将所有条件用 and 联合起来
					if (!predicates.isEmpty()) {
						return builder.and(predicates.toArray(new Predicate[predicates.size()]));
					}
				}

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

注意：IN 关键字的处理与其他不同