Spring Data Jpa多表查询如何返回自定义实体

小编给大家分享一下Spring Data Jpa多表查询如何返回自定义实体，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！

SpringDataJpa多表查询返回自定义实体

比如来看一下这样的一条SQL语句，这是一个三张表的多表查询，显然在JPA中用一个实体类是接受不了这些参数的

select t1.id as chapterId ,t1.name as chapterName ,t2.id as unitId,t2.name as unitName ,t3.id as lessonId,t3.name as lessonNamefrom  t_chapter t1LEFT JOIN  t_unit t2 on t1.id =t2.chapter_idLEFT JOIN t_lession t3 on t3.unit_id =t2.id where t1.id= '4028b4816305ea91016305eec24f0000' and t2.id='4028b4816305f1a6016305f423180000'and t3.id= '4028b4816306007b016306020bb80000';

Repository

/** * Created by ZhuPengWei on 2018/5/11. */public interface TestRepository extends JpaRepository {    @Query(            value = "select \n" +                    "t1.id as chapterId ,t1.name as chapterName ,t2.id as unitId,t2.name as unitName ,t3.id as lessonId,t3.name as lessonName\n" +                    "from  t_chapter t1\n" +                    "LEFT JOIN  t_unit t2 on t1.id =t2.chapter_id\n" +                    "LEFT JOIN t_lession t3 on t3.unit_id =t2.id \n" +                    "where t1.id= :chapterId \n" +                    "and t2.id=:unitId \n" +                    "and t3.id= :lessonId",            nativeQuery = true    )    List select(@Param("chapterId") String chapterId, @Param("unitId") String unitId, @Param("lessonId") String lessonId);}

好下面到单元测试

/** * Created by ZhuPengWei on 2018/5/11. */@RunWith(SpringRunner.class)@SpringBootTestpublic class TestRepositoryTest {    @Autowired    private TestRepository testRepository;    @Test    public void select() throws Exception {        List select = testRepository.select("4028b4816305ea91016305eec24f0000", "4028b4816305f1a6016305f423180000", "4028b4816306007b016306020bb80000");        List testViews = castEntity(select, TestView.class);        Assert.assertTrue(testViews.size() > 0);    }    //转换实体类   public static  List castEntity(List list, Class clazz) throws Exception {        List returnList = new ArrayList();        if(CollectionUtils.isEmpty(list)){            return returnList;        }        Object[] co = list.get(0);        Class[] c2 = new Class[co.length];        //确定构造方法        for (int i = 0; i < co.length; i++) {            if(co[i]!=null){                c2[i] = co[i].getClass();            }else {                c2[i]=String.class;            }        }        for (Object[] o : list) {            Constructor constructor = clazz.getConstructor(c2);            returnList.add(constructor.newInstance(o));        }        return returnList;    }

自定义实体

/** * Created by ZhuPengWei on 2018/5/11. */@Datapublic class TestView {    private String chapterId;    private String chapterName;    private String unitId;    private String unitName;    private String lessonId;    private String lessonName;    public TestView() {    }    public TestView(String chapterId, String chapterName, String unitId, String unitName, String lessonId, String lessonName) {        this.chapterId = chapterId;        this.chapterName = chapterName;        this.unitId = unitId;        this.unitName = unitName;        this.lessonId = lessonId;        this.lessonName = lessonName;    }}

需要注意的是 SQL语句的字段顺序一定要与实体类字段的顺序保持一致，否则会出现参数封装错误的情况

Spring Data Jpa多表查询返回自定义VO的问题

这两天开了一个新项目，使用SpringBoot+SpringData， 刚做了一个小功能，都是一张表的操作没什么问题，今天设计到了两张表联查，两张表各取了几个字段，组合成了一个vo， 当我用原生sql查询时报出 "找不到转换器"，当我用JPQL查询时，报出 xxx is not mapped.。 着实浪费了些时间。

其实最大的根本原因在于， 当使用JPQL 查询时，我们 FROM 的表名就不能是实体上@Table 注解中的表名，而是对应的实体的类名，记住是类名，并且查询的字段要是 实体类的属性，而不是数据库字段。切记。

下面是我的代码

package com.wisdombud.dama.quality.datasource.pojo;import java.io.Serializable;import java.util.Date;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.SequenceGenerator;import javax.persistence.Table;import javax.validation.constraints.NotBlank;import com.fasterxml.jackson.annotation.JsonFormat;import lombok.ToString;@Entity@Table(name = "DATA_SOURCE")@SequenceGenerator(name = "ID_SEQ", sequenceName = "SEQ_DATA_SOURCE", allocationSize = 1)@ToStringpublic class DataSourcePojo implements Serializable{    private static final long serialVersionUID = 4658654420795590006L;        private Long id;        @NotBlank(message = "数据源名称不能为空！")    private String name;        @NotBlank(message = "ip地址不能为空！")    private String ip;        @NotBlank(message = "端口号不能为空！")    private String port;        @NotBlank(message = "服务名不能为空！")    private String serviceName;        @NotBlank(message = "用户名不能为空！")    private String userName;        @NotBlank(message = "密码不能为空！")    private String password;    private String managerBranch;    private String leadingCadre;    private String phone;    private Long sortIndex;    private String remark;    private Long createUserId;    private String createUserName;        @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "GMT+8")    private Date createTime;    private Date lastUpdateTime;    private String re1;    private String re2;    private String re3;    private String re4;        @Id    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "ID_SEQ")    @Column(name = "ID", unique = true, nullable = false, precision = 18, scale = 0)    public Long getId() {        return id;    }    public void setId(Long id) {        this.id = id;    }        @Column(name = "NAME")    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }        @Column(name = "IP")    public String getIp() {        return ip;    }    public void setIp(String ip) {        this.ip = ip;    }        @Column(name = "PORT")    public String getPort() {        return port;    }    public void setPort(String port) {        this.port = port;    }        @Column(name = "SERVICE_NAME")    public String getServiceName() {        return serviceName;    }    public void setServiceName(String serviceName) {        this.serviceName = serviceName;    }        @Column(name = "USER_NAME")    public String getUserName() {        return userName;    }    public void setUserName(String userName) {        this.userName = userName;    }        @Column(name = "PASSWORD")    public String getPassword() {        return password;    }    public void setPassword(String password) {        this.password = password;    }        @Column(name = "MANAGER_BRANCH")    public String getManagerBranch() {        return managerBranch;    }    public void setManagerBranch(String managerBranch) {        this.managerBranch = managerBranch;    }        @Column(name = "LEADING_CADRE")    public String getLeadingCadre() {        return leadingCadre;    }    public void setLeadingCadre(String leadingCadre) {        this.leadingCadre = leadingCadre;    }        @Column(name = "PHONE")    public String getPhone() {        return phone;    }    public void setPhone(String phone) {        this.phone = phone;    }        @Column(name = "SORT_INDEX")    public Long getSortIndex() {        return sortIndex;    }    public void setSortIndex(Long sortIndex) {        this.sortIndex = sortIndex;    }        @Column(name = "REMARK")    public String getRemark() {        return remark;    }    public void setRemark(String remark) {        this.remark = remark;    }        @Column(name = "CREATE_USER_ID")    public Long getCreateUserId() {        return createUserId;    }    public void setCreateUserId(Long createUserId) {        this.createUserId = createUserId;    }        @Column(name = "CREATE_USER_NAME")    public String getCreateUserName() {        return createUserName;    }    public void setCreateUserName(String createUserName) {        this.createUserName = createUserName;    }        @Column(name = "CREATE_TIME")    public Date getCreateTime() {        return createTime;    }    public void setCreateTime(Date createTime) {        this.createTime = createTime;    }        @Column(name = "LAST_UPDATE_TIME")    public Date getLastUpdateTime() {        return lastUpdateTime;    }    public void setLastUpdateTime(Date lastUpdateTime) {        this.lastUpdateTime = lastUpdateTime;    }        @Column(name = "RE1")    public String getRe1() {        return re1;    }    public void setRe1(String re1) {        this.re1 = re1;    }        @Column(name = "RE2")    public String getRe2() {        return re2;    }    public void setRe2(String re2) {        this.re2 = re2;    }        @Column(name = "RE3")    public String getRe3() {        return re3;    }    public void setRe3(String re3) {        this.re3 = re3;    }        @Column(name = "RE4")    public String getRe4() {        return re4;    }    public void setRe4(String re4) {        this.re4 = re4;    }}

package com.wisdombud.dama.quality.datasource.tablerelation.pojo;import java.io.Serializable;import java.util.Date;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.SequenceGenerator;import javax.persistence.Table;import lombok.ToString;/** * 表关系实体 * @author qiaoyutao * @Date: 2019年7月4日 上午11:40:10 */@Entity@Table(name = "TABLE_RELATION")@SequenceGenerator(name = "ID_SEQ", sequenceName = "SEQ_TABLE_RELATION", allocationSize = 1)@ToStringpublic class TableRelationPojo implements Serializable{    private static final long serialVersionUID = -9058973373224769393L;        private Long id;    private Long dataSourceId;    private String tableName;    private String columnName;    private String relationTableName;    private String relationColumnName;    private String remark;    private Long createUserId;    private String createUserName;    private Date createTime;    private Date lastUpdateTime;    private String re1;    private String re2;    private String re3;    private String re4;        @Id    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "ID_SEQ")    @Column(name = "ID", unique = true, nullable = false, precision = 18, scale = 0)    public Long getId() {        return id;    }    public void setId(Long id) {        this.id = id;    }        @Column(name = "DATA_SOURCE_ID")    public Long getDataSourceId() {        return dataSourceId;    }    public void setDataSourceId(Long dataSourceId) {        this.dataSourceId = dataSourceId;    }        @Column(name = "TABLE_NAME")    public String getTableName() {        return tableName;    }    public void setTableName(String tableName) {        this.tableName = tableName;    }        @Column(name = "COLUMN_NAME")    public String getColumnName() {        return columnName;    }    public void setColumnName(String columnName) {        this.columnName = columnName;    }        @Column(name = "RELATION_TABLE_NAME")    public String getRelationTableName() {        return relationTableName;    }    public void setRelationTableName(String relationTableName) {        this.relationTableName = relationTableName;    }        @Column(name = "RELATION_COLUMN_NAME")    public String getRelationColumnName() {        return relationColumnName;    }    public void setRelationColumnName(String relationColumnName) {        this.relationColumnName = relationColumnName;    }        @Column(name = "REMARK")    public String getRemark() {        return remark;    }    public void setRemark(String remark) {        this.remark = remark;    }        @Column(name = "CREATE_USER_ID")    public Long getCreateUserId() {        return createUserId;    }    public void setCreateUserId(Long createUserId) {        this.createUserId = createUserId;    }        @Column(name = "CREATE_USER_NAME")    public String getCreateUserName() {        return createUserName;    }    public void setCreateUserName(String createUserName) {        this.createUserName = createUserName;    }        @Column(name = "CREATE_TIME")    public Date getCreateTime() {        return createTime;    }    public void setCreateTime(Date createTime) {        this.createTime = createTime;    }        @Column(name = "LAST_UPDATE_TIME")    public Date getLastUpdateTime() {        return lastUpdateTime;    }    public void setLastUpdateTime(Date lastUpdateTime) {        this.lastUpdateTime = lastUpdateTime;    }        @Column(name = "RE1")    public String getRe1() {        return re1;    }    public void setRe1(String re1) {        this.re1 = re1;    }        @Column(name = "RE2")    public String getRe2() {        return re2;    }    public void setRe2(String re2) {        this.re2 = re2;    }        @Column(name = "RE3")    public String getRe3() {        return re3;    }    public void setRe3(String re3) {        this.re3 = re3;    }        @Column(name = "RE4")    public String getRe4() {        return re4;    }    public void setRe4(String re4) {        this.re4 = re4;    }}

下面是我的dao层，重点

package com.wisdombud.dama.quality.datasource.tablerelation.dao;import org.springframework.data.domain.Page;import org.springframework.data.domain.Pageable;import org.springframework.data.jpa.repository.JpaRepository;import org.springframework.data.jpa.repository.JpaSpecificationExecutor;import org.springframework.data.jpa.repository.Query;import com.wisdombud.dama.quality.datasource.tablerelation.pojo.TableRelationPojo;import com.wisdombud.dama.quality.datasource.tablerelation.vo.TableRelationGridVo;public interface TableRelationDao extends JpaRepository, JpaSpecificationExecutor{        // 这里使用JPQL来写的， 区别就是 new 一个vo名，最好带上全路径，并且vo中要有有参构造器，构造器签名要与查询的字段一致, 查询的属性都是实体类中的属性名，不是数据库的字段名，这点切记。    @Query(value = "SELECT new com.wisdombud.dama.quality.datasource.tablerelation.vo.TableRelationGridVo(re.id, "            + "ds.name, re.tableName, re.columnName, "            + "re.relationTableName, re.relationColumnName, "            + "re.createTime) "            + "FROM TableRelationPojo re left join DataSourcePojo ds on re.dataSourceId = ds.id")    public Page page(Pageable pageable);    }

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