JPA 多条件、多表查询

JPA对于简单的查询操作确实很给力，但是涉及到多表、多条件、分页的场景就不是很好实现了。

可行的解决方案

1、多条件

public interface BaseRepository<T,ID extends Serializable> extends JpaRepository<T,ID>, JpaSpecificationExecutor<T>

使用Specification来实现条件的拼接

2、多表

数据量不大的情况，可以考虑视图，视图实体配置和表的没有任何区别。

3、分页

可以自行实现分页逻辑，也可以使用框架的 Pageable 类。

核心代码示例

//   核心方法 拼接条件public default Predicate getPredocate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb,DataQueryObject dqo) {List<Predicate> predicates = new ArrayList<>();
//      获取查询对象的所有属性Field[] fields = dqo.getClass().getDeclaredFields();for (Field field : fields) {field.setAccessible(true);String queryFiled = null;QueryType queryType = null;Object value = null;Predicate predicate = null;
//          获取属性的 自定义注解类型QueryField annotaion = field.getAnnotation(QueryField.class);
//          如果没有注解 则跳过if(annotaion == null) {continue;}
//          如果注解中 name为空 则用字段名称作为属性名if(!StringUtils.isEmpty(annotaion.name())) {queryFiled = annotaion.name();} else {queryFiled = field.getName();}queryType = annotaion.type();try {value = field.get(dqo);} catch (IllegalArgumentException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();}
//          判断字段类型是否为空if(value == null && queryType.isNotCanBeNull()) {logger.debug("查询类型：" + queryType + "不允许为空。");continue;}
//          判断注解中 的条件类型switch (queryType) {case EQUAL:Path<Object> equal = getRootByQueryFiled(queryFiled, root);predicate = cb.equal(equal, value);predicates.add(predicate);break;case BEWTEEN:Path<Comparable> between = getRootByQueryFiledComparable(queryFiled, root);QueryBetween queryBetween = null;if(value instanceof QueryBetween) queryBetween = (QueryBetween) value;else continue;predicate = cb.between(between, queryBetween.after, queryBetween.before);predicates.add(predicate);break;case LESS_THAN:Path<Comparable> lessThan = getRootByQueryFiledComparable(queryFiled, root);if(value instanceof QueryBetween) queryBetween = (QueryBetween) value;else continue;predicate = cb.lessThan(lessThan, queryBetween.after);predicates.add(predicate);break;case LESS_THAN_EQUAL:Path<Comparable> lessThanOrEqualTo = getRootByQueryFiledComparable(queryFiled, root);if(value instanceof QueryBetween) queryBetween = (QueryBetween) value;else continue;predicate = cb.lessThanOrEqualTo(lessThanOrEqualTo, queryBetween.after);predicates.add(predicate);break;case GREATEROR_THAN:Path<Comparable> greaterThan = getRootByQueryFiledComparable(queryFiled, root);if(value instanceof QueryBetween) queryBetween = (QueryBetween) value;else continue;predicate = cb.greaterThan(greaterThan, queryBetween.after);predicates.add(predicate);break;case GREATEROR_THAN_EQUAL:Path<Comparable> greaterThanOrEqualTo = getRootByQueryFiledComparable(queryFiled, root);if(value instanceof QueryBetween) queryBetween = (QueryBetween) value;else continue;predicate = cb.lessThanOrEqualTo(greaterThanOrEqualTo, queryBetween.after);predicates.add(predicate);break;case NOT_EQUAL:Path<Object> notEqual = getRootByQueryFiled(queryFiled, root);predicate = cb.notEqual(notEqual, value);predicates.add(predicate);break;case IS_NULL:Path<Object> isNull = getRootByQueryFiled(queryFiled, root);predicate = cb.isNull(isNull);predicates.add(predicate);break;case IS_NOT_NULL:Path<Object> isNotNull = getRootByQueryFiled(queryFiled, root);predicate = cb.isNotNull(isNotNull);predicates.add(predicate);break;case LEFT_LIKE:Path<String> leftLike = getRootByQueryFiledString(queryFiled, root);predicate = cb.like(leftLike, "%" + value.toString());predicates.add(predicate);break;case RIGHT_LIKE:Path<String> rightLike = getRootByQueryFiledString(queryFiled, root);predicate = cb.like(rightLike, value.toString() + "%");predicates.add(predicate);break;case FULL_LIKE:Path<String> fullLike = getRootByQueryFiledString(queryFiled, root);predicate = cb.like(fullLike, "%" + value.toString() + "%");predicates.add(predicate);break;case DEFAULT_LIKE:Path<String> like = getRootByQueryFiledString(queryFiled, root);predicate = cb.like(like, value.toString());predicates.add(predicate);break;case NOT_LIKE:Path<String> notLike = getRootByQueryFiledString(queryFiled, root);predicate = cb.like(notLike, value.toString());predicates.add(predicate);break;case IN:Path<Object> in = getRootByQueryFiled(queryFiled, root);In ins = cb.in(in);List inList = null;if(value instanceof List) {inList = (List) value;}for (Object object : inList) {ins.value(object);}predicates.add(ins);break;default:break;}}
//      如果 为空 代表  没有任何有效的条件if(predicates.size() == 0) {return cb.and();}Object[] list = predicates.toArray();Predicate[] t = new Predicate[predicates.size()];Predicate[] result = predicates.toArray(t);return cb.and(result);}public default Path<Object> getRootByQueryFiled(String queryFiled, Root<T> root) {if(queryFiled.indexOf(".") < 0) {return root.get(queryFiled);} else {return getRootByQueryFiled(queryFiled.substring(queryFiled.indexOf(".") + 1, queryFiled.length()), root.get(queryFiled.substring(0, queryFiled.indexOf("."))));}}public default Path<Object> getRootByQueryFiled(String queryFiled, Path<Object> path) {if(queryFiled.indexOf(".") < 0) {return path.get(queryFiled);} else {return getRootByQueryFiled(queryFiled.substring(queryFiled.indexOf(".") + 1, queryFiled.length()), path.get(queryFiled.substring(0, queryFiled.indexOf("."))));}}public default Path<String> getRootByQueryFiledString(String queryFiled, Root<T> root) {if(queryFiled.indexOf(".") < 0) {return root.get(queryFiled);} else {return getRootByQueryFiledString(queryFiled.substring(queryFiled.indexOf(".") + 1, queryFiled.length()), root.get(queryFiled.substring(0, queryFiled.indexOf("."))));}}public default Path<String> getRootByQueryFiledString(String queryFiled, Path<Object> path) {if(queryFiled.indexOf(".") < 0) {return path.get(queryFiled);} else {return getRootByQueryFiledString(queryFiled.substring(queryFiled.indexOf(".") + 1, queryFiled.length()), path.get(queryFiled.substring(0, queryFiled.indexOf("."))));}}public default Path<Comparable> getRootByQueryFiledComparable(String queryFiled, Root<T> root) {if(queryFiled.indexOf(".") < 0) {return root.get(queryFiled);} else {return getRootByQueryFiledComparable(queryFiled.substring(queryFiled.indexOf(".") + 1, queryFiled.length()), root.get(queryFiled.substring(0, queryFiled.indexOf("."))));}}public default Path<Comparable> getRootByQueryFiledComparable(String queryFiled, Path<Object> path) {if(queryFiled.indexOf(".") < 0) {return path.get(queryFiled);} else {return getRootByQueryFiledComparable(queryFiled.substring(queryFiled.indexOf(".") + 1, queryFiled.length()), path.get(queryFiled.substring(0, queryFiled.indexOf("."))));}}

自定义注解

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface QueryField {QueryType type();String name() default "";
}

接收参数

 @QueryField(type = QueryType.EQUAL, name = "redddlCode")@ApiModelProperty(value="XXX",name="redddlCode",example="S2344")private String redddlCode;

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