JPA生成全属性条件查询通用Specification

素颜马尾好姑娘i 2022-11-08 11:49 255阅读 0赞

## 1、使用Specification+JPA不作封装的时候每次都要挨个判断属性，很是麻烦 ##

**以下对生成Specification做一个封装**

/**
         * 生成全属性条件查询通用Specification
         *
         * @param tableMap    属性参数
         * @param clazz       要查询的实体类或vo类
         * @param excludeAttr 不使用模糊搜索的字符串属性
         * @param map         外键关联查询
         * @param <S>
         * @return
         */
        public <S> Specification<S> createSpecification(Map<String, String> tableMap, Class clazz, List<String> excludeAttr, Map map) { 
            Specification<S> specification = (root, query, cb) -> { 
                List<Predicate> predicates = new ArrayList<>();
    
                //未删除的数据
                try { 
                    clazz.getDeclaredField(Constants.VALID);
                    if (!StringUtils.isEmpty(tableMap.get(Constants.VALID))) { 
                        predicates.add(cb.equal(root.get(Constants.VALID), Integer.valueOf(tableMap.get(Constants.VALID))));
                    } else { 
                        predicates.add(cb.equal(root.get(Constants.VALID), 1));
                    }
                } catch (NoSuchFieldException e) { 
                    logger.warn("没有找到 {valid} 属性");
                }
    
                Field[] declaredFields = clazz.getDeclaredFields();
    
                if (tableMap != null) { 
                    for (Field field : declaredFields) { 
                        String fieldName = field.getName();
                        if (!StringUtils.isEmpty(tableMap.get(fieldName))) { 
                            String typeName = field.getGenericType().getTypeName();
                            Class<?> aClass = null;
                            try { 
                                aClass = Class.forName(typeName);
                            } catch (ClassNotFoundException e) { 
                                e.printStackTrace();
                            }
                            //属性不包含特定的属性并且是字符串采用模糊搜索
                            if (aClass == String.class && (CollectionUtils.isEmpty(excludeAttr) || !excludeAttr.contains(fieldName))) { 
                                String queryFieldName = "%" + tableMap.get(fieldName).replace("/", "\\/")
                                        .replaceAll("_", "\\\\_").replaceAll("%", "\\\\%") + "%";
                                predicates.add(cb.like(root.get(fieldName), queryFieldName));
                            } else { 
                                predicates.add(cb.equal(root.get(fieldName), tableMap.get(fieldName)));
                            }
                        }
                    }
                    if (!CollectionUtils.isEmpty(map)) { 
                        Iterator iterator = map.keySet().iterator();
                        while (iterator.hasNext()) { 
                            String sourceKey = iterator.next().toString();
                            Map mapping = (Map) map.get(sourceKey);
                            Join join = root.join(sourceKey, JoinType.INNER);
                            Iterator mappingItr = mapping.keySet().iterator();
                            while (mappingItr.hasNext()) { 
                                String joinKey = mappingItr.next().toString();
                                String joinAttr = mapping.get(joinKey).toString();
                                if (!StringUtils.isEmpty(tableMap.get(joinKey))) { 
                                    predicates.add(cb.equal(join.get(joinAttr), tableMap.get(joinKey)));
                                }
                            }
                        }
                    }
                }
                Predicate[] pre = new Predicate[predicates.size()];
                Predicate preAnd = cb.and(predicates.toArray(pre));
                return query.where(preAnd).getRestriction();
            };
            return specification;
        }

## 2、使用方式 ##

Map<String, Map<String, String>> joinAttr = new HashMap(4);
            //mapping为请求参数与实体属性名之间的映射关系
            Map mapping = new HashMap(4);
            mapping.put("tankAreaId", "id");
            mapping.put("tankAreaCode", "tankAreaCode");
             //joinAttr为当前实体关联字段名称
            joinAttr.put("tankArea", mapping);
            Specification<TankMovementEntity> specification = reflectUtil.createSpecification(tableMap, TankMovementVo.class, null, createJoinField());

## 3、很方便，不需要再一个一个去判断 ##

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JPA生成全属性条件查询通用Specification

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