實現

PagingAndSortingRepository,
QueryDslPredicateExecutor,
JpaSpecificationExecutor

寫了一個封裝類，封裝了查詢通用條件
1、實現動態綁定entity任意屬性去查詢或者排序
2、也適用于update的話，只更新請求傳過來的值去update，其他不變
3、動態構建PageRequest，實現多重排序條件
4、動態構建Specification， 實現多重條件查詢
下面實例代碼：

package base

import com.alibaba.fastjson.JSON
import com.alibaba.fastjson.JSONObject
import com.querydsl.core.types.ExpressionUtils
import com.querydsl.core.types.Ops
import com.querydsl.core.types.Predicate
import com.querydsl.core.types.dsl.BooleanExpression
import com.querydsl.core.types.dsl.Expressions
import com.querydsl.core.types.dsl.StringPath
import org.springframework.data.domain.PageRequest
import org.springframework.data.domain.Sort
import org.springframework.data.jpa.domain.Specification
import org.springframework.web.bind.annotation.ExceptionHandler
import java.io.BufferedReader
import java.lang.reflect.Method
import java.util.ArrayList
import javax.persistence.criteria.CriteriaBuilder
import javax.persistence.criteria.CriteriaQuery
import javax.persistence.criteria.Root


/**
 * Created by liushuhua on 25/03/2017.
 *
 * @ControllerAdvice will only kick in if an exception is thrown from within a controller method
 *
 **/

internal class EntityBuilder {
    companion object Factory {

        /**
         * 構造query條件的Expression
         * 將傳遞的參數自動綁定到Entity上
         *
         * @param  Any
         * @return BooleanExpression
         */
        @ExceptionHandler(Throwable::class)
        fun matchSelectiveAttrExpressions(obj: Any): BooleanExpression? {
            val c = obj.javaClass
            var rv: BooleanExpression? = null
            val fs = c.getDeclaredFields()
            for (i in fs.indices) {
                val f = fs[i]
                f.isAccessible = true //設置些屬性是可以訪問的
                val `val` = f.get(obj)//得到此屬性的值
                if (`val` != null) {
                    val ce1 = Expressions.stringPath(lowerCaseClassName(c.getSimpleName()) + "." + f.name)
                    val ce2 = ExpressionUtils.toExpression(`val`)
                    val pred = Expressions.booleanOperation(Ops.EQ, ce1, ce2)
                    rv = if (rv != null) rv.and(pred) else pred
                }
            }

            return rv
        }

        /**
         * 構造update的Enity
         * 將傳遞的參數綁定到該id的Entity上，
         * 設置成新的Entity，id不變，再到數據庫update
         *
         * @param Any1, Any2
         * @return Any2
         */
        @Throws(Exception::class)
        fun matchSelectiveEntity(obj1: Any, obj2: Any): Any {
            val fields = obj1.javaClass.declaredFields
            // 遍歷所有屬性
            for (j in fields.indices) {
                val name = fields[j].name
                if (fields[j].get(obj1) != null && !"createdAt".equals(name) && !"createdBy".equals(name)) {
                    val args = arrayOfNulls<Class<*>>(1)
                    args[0] = fields[j].type
                    val c = obj1.javaClass
                    val methodName = "set" + upperCaseClassName(name)
                    var method: Method? = null
                    method = c.getMethod(methodName, *args)
                    method!!.invoke(obj2, fields[j].get(obj1))
                }
            }
            return obj2
        }

        /**
         * 創建分頁請求.
         * pageNumber 從 1 開始
         */
        @Throws(Exception::class)
        fun buildPageRequest(jsonObject: JSONObject): PageRequest {
            val pageNumber = Integer.parseInt(jsonObject["pageNumber"].toString())
            val pagzSize = Integer.parseInt(jsonObject["pageSize"].toString())

            val sortArray = jsonObject.getJSONArray("sort")
            val sortList = ArrayList<Sort.Order>()
            for (i in sortArray.indices) {
                val ascFlag = sortArray.getJSONObject(i)["asc"].toString()
                var order: Sort.Order? = null
                if ("true" == ascFlag) {
                    order = Sort.Order(Sort.Direction.ASC, sortArray.getJSONObject(i)["field"].toString())
                } else {
                    order = Sort.Order(Sort.Direction.DESC, sortArray.getJSONObject(i)["field"].toString())
                }
                sortList.add(order)
            }
            return PageRequest(pageNumber - 1, pagzSize, Sort(sortList))
        }

        /**
         * 創建動態查詢條件組合.
         */
        @Throws(Exception::class)
        fun <T> buildSpecification(jsonObject: JSONObject): Specification<T> {
            val criteriaArray = jsonObject.getJSONArray("criteria")
            val spec = Specification<T> { root, criteriaQuery, criteriaBuilder ->
                val predicates = ArrayList<javax.persistence.criteria.Predicate>()
                for (i in criteriaArray.indices) {
                    val field = criteriaArray.getJSONObject(i)["field"].toString()
                    val value = criteriaArray.getJSONObject(i)["value"].toString()
                    val operator = criteriaArray.getJSONObject(i)["operator"].toString()

                    if ("eq" == operator) {
                        predicates.add(criteriaBuilder.equal(root.get<Any>(field), value))
                    }
                }
                criteriaBuilder.and(*predicates.toTypedArray())
            }
            return spec
        }


        private fun lowerCaseClassName(name: String): String {
            return name.substring(0, 1).toLowerCase() + name.substring(1)
        }

        private fun upperCaseClassName(name: String): String {
            return name.substring(0, 1).toUpperCase() + name.substring(1)
        }
    }
}

調用查詢方法

override fun listCustomer(jsonObject: JSONObject): MutableIterable<Customer> {
    val pageable = EntityBuilder.buildPageRequest(jsonObject)
    val spec = EntityBuilder.buildSpecification<Customer>(jsonObject)
    return customerRepository.findAll(spec, pageable)
}

其中jsonObject是：
{
  "pageNumber": "1",
  "pageSize": "10",
  "criteria": [{"operator": "like", "field": "name", "value": "aaa"}],
  "sort": [{"field":"id","asc":"true"}]
}

調用更新方法

override fun save(customer: Customer) : Customer {
    if(customer.id == null){
        return customerRepository.save(customer)
    }else{
        val oldCustomer = findById(customer.id)
        if(oldCustomer == null){
            throw Exception("The entity not found")
        }
        val customer = EntityBuilder.matchSelectiveEntity(customer, oldCustomer!!) as Customer
        return customerRepository.save(customer)
    }
}