概述

　　ORM映射為我們帶來便利的同時，也失去了較大靈活性，如果SQL較復雜，要進行動態查詢，那必定是一件頭疼的事情（也可能是lz還沒發現好的方法），記錄下自己用的三種復雜查詢方式。

環境

springBoot

IDEA2017.3.4

JDK8

pom.xml

<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.1.6.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.xmlxy</groupId><artifactId>seasgame</artifactId><version>0.0.1-SNAPSHOT</version><name>seasgame</name><description>Demo project for Spring Boot</description><properties><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><!--數據庫連接--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope></dependency><!-- 熱啟動等 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-devtools</artifactId><scope>runtime</scope><optional>true</optional></dependency><!--Java bean 實體--><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId></dependency><!--swagger2 API 測試工具 --><dependency><groupId>io.springfox</groupId><artifactId>springfox-swagger2</artifactId><version>2.8.0</version></dependency><dependency><groupId>io.springfox</groupId><artifactId>springfox-swagger-ui</artifactId><version>2.8.0</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-configuration-processor</artifactId><optional>true</optional></dependency><!--安全框架認證--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-security</artifactId></dependency><dependency><groupId>net.sf.json-lib</groupId><artifactId>json-lib</artifactId><version>2.2.2</version><classifier>jdk15</classifier></dependency><!--漢字轉拼音--><dependency><groupId>com.belerweb</groupId><artifactId>pinyin4j</artifactId><version>2.5.1</version></dependency><!-- thymeleaf模板 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-thymeleaf</artifactId></dependency><!--<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId>移除嵌入式tomcat插件<exclusions><exclusion><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-tomcat</artifactId></exclusion></exclusions></dependency>--><dependency><groupId>javax.servlet</groupId><artifactId>javax.servlet-api</artifactId><version>3.1.0</version><scope>provided</scope></dependency></dependencies><packaging>war</packaging><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><configuration><source>1.8</source><target>1.8</target></configuration></plugin></plugins><finalName>seasgame</finalName><pluginManagement><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><version>2.3.2</version><configuration><encoding>${project.build.sourceEncoding}</encoding><source>1.7</source><target>1.7</target></configuration></plugin><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-surefire-plugin</artifactId><configuration><testFailureIgnore>true</testFailureIgnore></configuration></plugin></plugins></pluginManagement></build></project>

@Query

當一個SQL較為復雜時，第一個想到的就是原生的SQL語句。如果只是簡單的查詢，那情況還沒這么糟糕

@Query(value = " SELECT IFNULL(sum(right_num),0) sumRight FROM t_record WHERE record_owner_id = ?1 AND responder_no = ?2 ",nativeQuery = true)Map<String,Object> sumRightNum(int studentId,int responderNo);

但如果需要進行動態查詢，或更改，那這個value就變得復雜了。

package com.xmlxy.seasgame.dao;import com.xmlxy.seasgame.entity.ScoreEntity; import org.springframework.data.jpa.repository.Modifying; import org.springframework.data.jpa.repository.Query; import org.springframework.data.repository.CrudRepository; import org.springframework.data.repository.query.Param; import org.springframework.transaction.annotation.Transactional;import java.util.List;/*** * Description: * @author hwc* @date 2019/9/5* @return */ public interface ScoreDao extends CrudRepository<ScoreEntity,Integer> {/** * * Description:*@param scoreEntity* @author hwc* @date 2019/9/6*/@Transactional(rollbackFor = Exception.class)@Modifying@Query(value = "UPDATE t_score t SET " +"t.responder_no = CASE WHEN :#{#scoreEntity.responderNo} IS NULL THEN t.responder_no ELSE :#{#scoreEntity.responderNo} END," +"t.max_level = CASE WHEN :#{#scoreEntity.maxLevel} IS NULL THEN t.max_level ELSE :#{#scoreEntity.maxLevel} END," +"t.right_num = CASE WHEN :#{#scoreEntity.rightNum} IS NULL THEN t.right_num ELSE :#{#scoreEntity.rightNum} END," +"t.use_time = CASE WHEN :#{#scoreEntity.userTime} IS NULL THEN t.use_time ELSE :#{#scoreEntity.userTime} END WHERE student_id = :#{#scoreEntity.getStudentId()}",nativeQuery = true)void updateScore(@Param("scoreEntity") ScoreEntity scoreEntity); }

JPQL

如果Java代碼內發出JPQL查詢，就需要利用到EntityManager的響應方法了。一般執行以下流程

獲取一個EntityManager實例

調用實例的方法createQuery，創建一個Query實例，如果有需要可以指定檢索的最大數量和起始位置

使用Query方法getResultList執行查詢，當然更新和刪除操作得使用executeUpdate執行

進行一個復雜的動態SQL查詢

public Page<RankEntity> getScoreByRank(int gradeId,int classId,Pageable pageable){StringBuilder countSelectSql = new StringBuilder("");countSelectSql.append(" SELECT COUNT(*) ");countSelectSql.append(" FROM ");countSelectSql.append(" t_score s, ");countSelectSql.append(" t_student st ");countSelectSql.append(" WHERE ");countSelectSql.append(" s.student_id = st.student_id ");StringBuilder selectSql = new StringBuilder();selectSql.append(" SELECT s.student_id,st.real_name,st.student_class,s.max_level,s.use_time,s.right_num ");selectSql.append(" FROM t_score s ");selectSql.append(" JOIN t_student st ON s.student_id = st.student_id ");selectSql.append(" WHERE 1 = 1 ");Map<String,Object> params = new HashMap<>();StringBuilder whereSql = new StringBuilder();if (gradeId != -1){whereSql.append(" AND st.student_grade = :student_grade ");params.put("student_grade",gradeId);}/**班級ID*/if (classId != -1){whereSql.append(" AND st.student_class = :classId ");params.put("classId",classId);}String orderSql = " ORDER BY s.max_level DESC,s.use_time,s.right_num ASC ";String countSql = new StringBuilder().append(countSelectSql).append(whereSql).toString();Query countQuery = entityManager.createNativeQuery(countSql);for (Map.Entry<String,Object> entry : params.entrySet()){countQuery.setParameter(entry.getKey(),entry.getValue());}BigInteger totalCount = (BigInteger)countQuery.getSingleResult();String querySql = new StringBuilder().append(selectSql).append(whereSql).append(orderSql).toString();Query query = entityManager.createNativeQuery(querySql,RankEntity.class);for (Map.Entry<String,Object> entry:params.entrySet()){query.setParameter(entry.getKey(),entry.getValue());}query.setFirstResult((int) pageable.getOffset());query.setMaxResults(pageable.getPageSize());List<RankEntity> rankEntities = query.getResultList();Page<RankEntity> page = new PageImpl<>(rankEntities,pageable,totalCount.longValue());return page;}

注意：如果沒有重新定義Pageable那么pageNumber必須減1，因為是從0開始的。

Criteria

這是一種規范查詢是以元模型的概念為基礎的，這個元模型可以是實體累，嵌入類，或者映射的父類，簡單介紹幾個里面用到接口。

CriteraQuery是一個特定的頂層查詢對象，里面包含select，from，where，order by等各個部分，然而他只對實體類或嵌入類的標準查詢起作用。

Root標準查詢的根對象，根定義了實體類型，是你想要查詢要獲得的結果，也可以添加查詢條件，結合實體管理對象得到查詢的對象。

CriteriaBuilder接口用來構建CritiaQuery的構建器

?StudentEntity類

package com.xmlxy.seasgame.entity;import io.swagger.annotations.ApiModel; import lombok.Data;import javax.persistence.*; import javax.print.attribute.standard.MediaSize; import java.io.Serializable;/*** * Description:學生對象* @param* @author hwc* @date 2019/8/8 */ @Entity @Table(name = "t_base_student") @ApiModel @Data public class StudentEntity implements Serializable {private static final long serialVersionUID = 546L;@Id@GeneratedValue(strategy = GenerationType.AUTO)@Column(name = "student_id")private Integer studentId;@Column(name = "student_grade")private Integer studentGrade;@Column(name = "student_class")private Integer studentClass;@Column(name = "address")private String address;@Column(name = "telephone")private Integer telephone;@Column(name = "real_name")private String realName;@Column(name = "id_number")private String idNumber;@Column(name = "study_id")private String studyId;@Column(name = "is_delete")private int isDelete;@Column(name = "uuid")private String uuid;}

dao層

public interface StudentDao extends JpaRepository<StudentEntity,Integer>,JpaSpecificationExecutor { }

動態查詢

public Page<StudentEntity> getTeacherClassStudent(int pageNumber,int pageSize,int gradeId, int classId,String keyword){pageNumber = pageNumber < 0 ? 0 : pageNumber;pageSize = pageSize < 0 ? 10 : pageSize;Specification<StudentEntity> specification = new Specification<StudentEntity>(){@Overridepublic Predicate toPredicate(Root<StudentEntity> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder){//page : 0 開始, limit : 默認為 10List<Predicate> predicates = new ArrayList<>();predicates.add(criteriaBuilder.equal(root.get("studentGrade"),gradeId));predicates.add(criteriaBuilder.equal(root.get("studentClass"),classId));if (!Constant.isEmptyString(keyword)){predicates.add(criteriaBuilder.like(root.get("realName").as(String.class),"%" + keyword + "%"));}return criteriaBuilder.and(predicates.toArray(new Predicate[predicates.size()]));}};/*studentId必須是實體類屬性與數據庫對應，否則報ropertyReferenceException異常*/PageRequest page = new PageRequest(pageNumber,pageSize,Sort.Direction.ASC,"studentId");Page<StudentEntity> pages = studentDao.findAll(specification,page);return pages;}

因為這個項目應用比較簡單，所以條件只有一個，如果條件較多，甚至可以定義一個專門的類去接收拼接參數，然后判斷，成立就add進去。

轉載一篇寫得不錯的文章：https://blog.csdn.net/u010775025/article/details/80497986

?

轉載于:https://www.cnblogs.com/dslx/p/11474453.html

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