项目背景：SpringBoot+jpa+h2数据库。
本菜鸟接了个需求，在数据库里增加一些数据。sql语句发过来了，如下所示：

INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('BH', 'ADDITIONAL_INFO', 'exam_report_additional_info.html', 'sa', '20140204 15:43:55', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('BH', 'CONTENT', 'exam_report_content.html', 'sa', '20140204 15:43:55', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('BH', 'FOOTER', 'exam_report_footer.html', 'sa', '20140204 15:43:55', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('BH', 'LAYOUT', 'exam_report_overlay.html', 'sa', '20140204 15:43:55', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('HCH', 'ADDITIONAL_INFO', 'exam_report_additional_info.html', 'syncdata', '20190122 12:05:38', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('HCH', 'CONTENT', 'exam_report_content.html', 'syncdata', '20190122 12:05:38', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('HCH', 'FOOTER', 'exam_report_footer.html', 'syncdata', '20190122 12:05:38', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('HCH', 'LAYOUT', 'exam_report_overlay.html', 'syncdata', '20190122 12:05:38', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('KH', 'ADDITIONAL_INFO', 'exam_report_additional_info.html', 'sa', '20140204 15:43:55', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('KH', 'CONTENT', 'exam_report_content.html', 'sa', '20140204 15:43:55', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('KH', 'FOOTER', 'exam_report_footer.html', 'sa', '20140204 15:43:55', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('KH', 'LAYOUT', 'exam_report_overlay.html', 'sa', '20140204 15:43:55', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('QEH', 'ADDITIONAL_INFO', 'exam_report_additional_info.html', 'sa', '20140204 15:43:55', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('QEH', 'CONTENT', 'exam_report_content.html', 'sa', '20140204 15:43:55', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('QEH', 'FOOTER', 'exam_report_footer.html', 'sa', '20140204 15:43:55', 'A');
INSERT INTO st_report_template(hosp_cde, section, path, last_upd_usr, last_upd_dt, status_cde) VALUES('QEH', 'LAYOUT', 'exam_report_overlay.html', 'sa', '20140204 15:43:55', 'A');

打眼一看，简单。cv一下，运行，报错：主键冲突。
再仔细看看，我把第一列当成主键，这么多重复的？？？！！！惊呆了，怎么办？
百度一番，使用jpa联合索引。
仔细看上面的sql语句：第一列很多重复的，但是第一列+第二列是不是就不重复了？怎么实现呢？上代码：

第一步，先写一个作为联合主键的实体类，把这两列放进来

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.NoArgsConstructor;

import java.io.Serializable;

@Data
@NoArgsConstructor
@AllArgsConstructor
@EqualsAndHashCode
public class StReportTemplatePK implements Serializable {

    private String hospCde;

    private String section;
}

第二步，写真正的实体类

import hk.org.ha.ris.primary.key.system.StReportTemplatePK;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.persistence.*;
import java.io.Serializable;

@Data
@Entity
//注意这个注解！！！！这个注解把联合主键的类放进来
@IdClass(StReportTemplatePK.class)
@Table(name = "st_report_template")
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class StReportTemplate implements Serializable {
    @Id//这个注解很重要，是联合主键其中的一个
    @Column(name = "hosp_cde", nullable = false,unique = false)
    private String hospCde;

    @Id//这个注解也很重要，是联合主键的另外一个
    @Column(name = "section", nullable = false)
    private String section;

    @Column(name = "path", nullable = false)
    private String path;

    @Column(name = "lastUpdUsr", nullable = false)
    private String lastUpdUsr;

    @Column(name = "lastUpdDt", nullable = false)
    private String lastUpdDt;

    @Column(name = "statusCde", nullable = false)
    private String statusCde;
}

注意看，这里的@Id注解已经不止一个，就是包含的这两列。

第三步，写repository

@Repository
public interface StReportTemplateRepository extends JpaRepository<StReportTemplate, StReportTemplatePK>, JpaSpecificationExecutor<StReportTemplate> {
}

完成。

注意坑：

命名一定要写规范，项目越来越大的情况下，前缀名都相同，很容易导错，错的多了血压都上来了。