jpa 分页查询几种demo Example分页/ExampleMatcher/Specification分页/SQL分页
作者：互联网
以下都是基于spring-data-jpa2.1.8
1.单纯分页，没有条件
/***
* 直接用dao调用分页
*/
@Test
public void findPageDao1() {
try {
System.out.println("=============== findPage ================" );
//jpa 1.*写法
//Pageable pageable = new PageRequest(0,2, Sort.Direction.DESC,"userId");//sprint-data-common 2.0以下用这个
//jpa 0.*写法 1
//Sort sort=Sort.by(Sort.Direction.DESC,"userId");
//Pageable pageable = PageRequest.of(0, 2,sort);
//jpa 0.*写法 2
Pageable pageable = PageRequest.of(0, 2, Sort.Direction.DESC,"userId");//一定要是model中的字段注意大小写,sprint-data-common 2.0以上用这个
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.(不推荐)使用findAll(example,pageable)Example/ExampleMatcher表达式分页 不支持 a=1 and (b=2 or c=3)这样的逻辑 https://stackoverflow.com/questions/42584191/spring-query-by-example-using-or
/***
* (不推荐)直接用dao调用分页带条件 Example<S> 不支持 a=1 and (b=2 or c=3)这样的逻辑 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");
//分页
int page=1;//第几页
int pageSize=2;//每页条数
//Pageable pageable = new PageRequest(page - 1, pageSize, sort);//已过时
Pageable pageable = PageRequest.of(page - 1, pageSize, sort);
//多条件 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，功能比较强大，可以实现常用的条件功能 Specification使用说明请参考：https://docs.spring.io/spring-data/jpa/docs/current/api/org/springframework/data/jpa/domain/Specification.html
/***
* 直接用dao调用分页带条件 Specification<S>
*/
@Test
public void findPageDao3() {
try {
System.out.println("=============== findPage ================" );
Sort sort = new Sort(Sort.Direction.DESC, "userId");
//分页
int page=1;//第几页
int pageSize=2;//每页条数
//Pageable pageable = new PageRequest(page - 1, pageSize, sort);//已过时
Pageable pageable = PageRequest.of(page - 1, pageSize, sort);
//多条件
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.自己写SQL条件返回List<Model>，这个最灵活可以随意写自己的SQL
/***
* 直接用dao调用分页带条件返回List<Model> 直接用SQL
*/
@Test
public void findPageDao4() {
try {
System.out.println("=============== findPage ================" );
//分页
int page=1;//第几页
int pageSize=2;//每页条数
//多条件
SysUser entity=new SysUser();
entity.setAccount("test");
entity.setUserName("zw1");
//查总数sql
String sqlCount="select count(*) from SYS_User where 1=1 and (account=:account or userName=:userName) Order by UserID desc ";
//查分页的数据
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;//记录总数
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.自己写SQL条件返回List<Map>，这个最灵活可以随意写自己的SQL
/***
* 直接用dao调用分页带条件返回List<Map> 直接用SQL
*/
@Test
public void findPageDao5() {
try {
System.out.println("=============== findPage ================" );
//分页
int page=1;//第几页
int pageSize=2;//每页条数
//多条件
SysUser entity=new SysUser();
entity.setAccount("test");
entity.setUserName("zw1");
//查总数sql
String sqlCount="select count(*) from SYS_User where 1=1 and (account=:account or userName=:userName) Order by UserID desc ";
//查分页的数据
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;//记录总数
Query query = sysUserService.getEntityManager().createNativeQuery(sql);//这时只有sql
query.unwrap(SQLQuery.class).setResultTransformer(Transformers.ALIAS_TO_ENTITY_MAP);//添加这一行才能返回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代码
@PersistenceContext
protected EntityManager em;// 类似hibernate session
//给子类用的
public EntityManager getEntityManager() {
return em;
}
SysUserDao代码
@Repository
public interface SysUserDao<SysUser,Integer> extends JpaRepository <T,ID>, JpaSpecificationExecutor<T> {
}
标签：分页,jpa,pageList,Specification,System,entity,println,page,out 来源： https://www.cnblogs.com/q149072205/p/12875771.html