jpa 分頁查詢幾種demo Example分頁/ExampleMatcher/Specification分頁/SQL分頁

以下都是基於spring-data-jpa2.1.8

1.單純分頁，沒有條件

/***
     * 直接用dao調用分頁
     */
    @Test
    public void findPageDao1() {
        try {
            System.out.println("=============== findPage ================" );

            //jpa 1.*寫法
            //Pageable pageable = new PageRequest(0,2, Sort.Direction.DESC,"userId");//sprint-data-common 2.0以下用這個
            //jpa 0.*寫法 1
            //Sort sort=Sort.by(Sort.Direction.DESC,"userId");
            //Pageable pageable = PageRequest.of(0, 2,sort);
            //jpa 0.*寫法 2
            Pageable pageable = PageRequest.of(0, 2, Sort.Direction.DESC,"userId");//一定要是model中的字段注意大小寫,sprint-data-common 2.0以上用這個
            Page<SysUser> pageList=sysUserDao.findAll(pageable);
            if(pageList!=null && pageList.getTotalPages()>0){
                System.out.println("page list:" );
                for(SysUser item:pageList){
                    System.out.println("userid: "+item.getUserId()+"__userAccount:"+item.getAccount());
                }
            }else {
                System.out.println("page is null:" );
            }
        } catch (Exception e) {
            System.out.println("error:" +e.getMessage());
            // e.printStackTrace();
        }
    }

2.(不推薦)使用findAll(example,pageable)Example/ExampleMatcher表達式分頁 不支持   a=1 and (b=2 or c=3)這樣的邏輯 https://stackoverflow.com/questions/42584191/spring-query-by-example-using-or

/***
     * (不推薦)直接用dao調用分頁帶條件  Example<S>  不支持   a=1 and (b=2 or c=3)這樣的邏輯 https://stackoverflow.com/questions/42584191/spring-query-by-example-using-or
     */
    @Test
    public void findPageDao2() {
        try {
            System.out.println("=============== findPage ================" );
            Sort sort = new Sort(Sort.Direction.DESC, "userId");
            //分頁
            int page=1;//第幾頁
            int pageSize=2;//每頁條數
            //Pageable pageable = new PageRequest(page - 1, pageSize, sort);//已過時
            Pageable pageable = PageRequest.of(page - 1, pageSize, sort);

            //多條件  account='test' and username='zw'
            SysUser entity=new SysUser();
            entity.setAccount("test");
            entity.setUserName("zw");
            ExampleMatcher matcher = ExampleMatcher.matching()
                    .withMatcher("account", ExampleMatcher.GenericPropertyMatchers.contains())
                    .withMatcher("userName", ExampleMatcher.GenericPropertyMatchers.contains());//like
            Example<SysUser> example = Example.of(entity,matcher);

            //Example<SysUser> example = Example.of(entity);

            Page<SysUser> pageList= sysUserDao.findAll(example,pageable);



            if(pageList!=null && pageList.getTotalPages()>0){
                System.out.println("page list:" );
                for(SysUser item:pageList){
                    System.out.println("userid: "+item.getUserId()+"__userAccount:"+item.getAccount());
                }
            }else {
                System.out.println("page is null:" );
            }
        } catch (Exception e) {
            System.out.println("error:" +e.getMessage());
            // e.printStackTrace();
        }
    }

3.使用Specification，功能比較強大，可以實現常用的條件功能  Specification使用說明請參考：https://docs.spring.io/spring-data/jpa/docs/current/api/org/springframework/data/jpa/domain/Specification.html

/***
     * 直接用dao調用分頁帶條件  Specification<S>
     */
    @Test
    public void findPageDao3() {
        try {
            System.out.println("=============== findPage ================" );
            Sort sort = new Sort(Sort.Direction.DESC, "userId");
            //分頁
            int page=1;//第幾頁
            int pageSize=2;//每頁條數
            //Pageable pageable = new PageRequest(page - 1, pageSize, sort);//已過時
            Pageable pageable = PageRequest.of(page - 1, pageSize, sort);

            //多條件
            SysUser entity=new SysUser();
            entity.setAccount("test");
            entity.setUserName("zw1");

            Specification<SysUser> spec=new Specification<SysUser>(){
                @Override
                public Predicate toPredicate(Root<SysUser> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                    Predicate p1 = cb.equal(root.get("account"), entity.getAccount());
                    Predicate p2 = cb.equal(root.get("userName"), entity.getUserName());
                    return cb.or(p1,p2);
                }
            };
            Page<SysUser> pageList= sysUserDao.findAll(spec,pageable);

            if(pageList!=null && pageList.getTotalPages()>0){
                System.out.println("page list:" );
                for(SysUser item:pageList){
                    System.out.println("userid: "+item.getUserId()+"__userAccount:"+item.getAccount());
                }
            }else {
                System.out.println("page is null:" );
            }
        } catch (Exception e) {
            System.out.println("error:" +e.getMessage());
            // e.printStackTrace();
        }
    }

4.自己寫SQL條件返回List<Model>，這個最靈活可以隨意寫自己的SQL

/***
     * 直接用dao調用分頁帶條件返回List<Model>  直接用SQL
     */
    @Test
    public void findPageDao4() {
        try {
            System.out.println("=============== findPage ================" );
            //分頁
            int page=1;//第幾頁
            int pageSize=2;//每頁條數

            //多條件
            SysUser entity=new SysUser();
            entity.setAccount("test");
            entity.setUserName("zw1");
            //查總數sql
            String sqlCount="select count(*) from SYS_User where 1=1  and (account=:account or userName=:userName) Order by UserID desc ";
            //查分頁的數據
            String sql="select * from SYS_User where 1=1   and (account=:account or userName=:userName) Order by UserID desc ";

            Query queryCount = sysUserService.getEntityManager().createNativeQuery(sqlCount);
            queryCount.setParameter("account", entity.getAccount());
            queryCount.setParameter("userName", entity.getUserName());
            Object count=queryCount.getSingleResult();
            Integer listCount = count != null ? Integer.parseInt(count.toString()) : 0;//記錄總數

            Query query = sysUserService.getEntityManager().createNativeQuery(sql,SysUser.class);//指定Model
            query.setParameter("account", entity.getAccount());
            query.setParameter("userName", entity.getUserName());
            int offSet = PageUtil.getOffset(page, pageSize);
            query.setFirstResult(offSet).setMaxResults(pageSize);
            List<SysUser> pageList=query.getResultList();

            if(pageList!=null && pageList.size()>0){
                System.out.println("page list:" +pageList.size());
                System.out.println("page Index:" +page+" item size :" +pageSize+" item Total :" +listCount);
                for(SysUser item:pageList){
                    System.out.println("userid: "+item.getUserId()+"__userAccount:"+item.getAccount());
                }
            }else {
                System.out.println("page is null:" );
            }
        } catch (Exception e) {
            System.out.println("error:" +e.getMessage());
            // e.printStackTrace();
        }
    }

4.自己寫SQL條件返回List<Map>，這個最靈活可以隨意寫自己的SQL

/***
     * 直接用dao調用分頁帶條件返回List<Map>  直接用SQL
     */
    @Test
    public void findPageDao5() {
        try {
            System.out.println("=============== findPage ================" );
            //分頁
            int page=1;//第幾頁
            int pageSize=2;//每頁條數

            //多條件
            SysUser entity=new SysUser();
            entity.setAccount("test");
            entity.setUserName("zw1");
            //查總數sql
            String sqlCount="select count(*) from SYS_User where 1=1  and (account=:account or userName=:userName) Order by UserID desc ";
            //查分頁的數據
            String sql="select * from SYS_User where 1=1   and (account=:account or userName=:userName) Order by UserID desc ";

            Query queryCount = sysUserService.getEntityManager().createNativeQuery(sqlCount);
            queryCount.setParameter("account", entity.getAccount());
            queryCount.setParameter("userName", entity.getUserName());
            Object count=queryCount.getSingleResult();
            Integer listCount = count != null ? Integer.parseInt(count.toString()) : 0;//記錄總數

            Query query = sysUserService.getEntityManager().createNativeQuery(sql);//這時只有sql
            query.unwrap(SQLQuery.class).setResultTransformer(Transformers.ALIAS_TO_ENTITY_MAP);//添加這一行才能返回List<Map>
            query.setParameter("account", entity.getAccount());
            query.setParameter("userName", entity.getUserName());
            int offSet = PageUtil.getOffset(page, pageSize);
            query.setFirstResult(offSet).setMaxResults(pageSize);
            List<Map> pageList=query.getResultList();

            if(pageList!=null && pageList.size()>0){
                System.out.println("page list:" +pageList.size());
                System.out.println("page Index:" +page+" item size :" +pageSize+" item Total :" +listCount);
                for(Map item:pageList){
                    System.out.println("userid: "+item.get("UserID").toString()+"__userAccount:"+item.get("Account").toString());
                }
            }else {
                System.out.println("page is null:" );
            }
        } catch (Exception e) {
            System.out.println("error:" +e.getMessage());
            // e.printStackTrace();
        }
    }

 

sysUserService代碼

@PersistenceContext
    protected EntityManager em;// 類似hibernate session

    //給子類用的
    public EntityManager getEntityManager() {
        return em;
    }

SysUserDao代碼

@Repository
public interface SysUserDao<SysUser,Integer> extends JpaRepository <T,ID>, JpaSpecificationExecutor<T> {

}