##springboot-jpa ####具体看test包下面的TestJpa单元类

主键查询

User user1 = userRepository.getOne(1L);

是否存在的id

userRepository.existsById(1L);

查询所有

List<User> all = userRepository.findAll();

查询符合主键的所有

List<Long> a = new ArrayList<>();
a.add(1L);
a.add(2L);
List<User> allById = userRepository.findAllById(a);

查询所有，id降序

List<User> id = userRepository.findAll(Sort.by("id").descending());

分页根据id降序查询

Pageable pageable =PageRequest.of(1,1, Sort.Direction.DESC,"id");
Page<User> page = userRepository.findAll(pageable);
System.out.println("总页数："+page.getTotalPages()+"当前页："+page.getPageable().getPageNumber());
User user=null;

保存或修改 立即 flush

userRepository.saveAndFlush(user);

保存或修改

userRepository.save(user);

批量保存

List<User> list=new ArrayList<>();
userRepository.saveAll(list);

删除单个

userRepository.delete(user);

删除所有，一条一条执行

userRepository.deleteAll();

单个删除

userRepository.deleteAll(list);

批量执行，一条语句

userRepository.deleteAllInBatch();

根据主键删除

userRepository.deleteById(1l);

批量删除

userRepository.deleteInBatch(list);

统计所有行数

long count = userRepository.count();

自定义方法的模糊查询

Page<User> admin4 = userRepository.findByUsernameLike("%admin%", PageRequest.of(0, 1, Sort.Direction.ASC, "username"));

QueryByExampleExecutor 接口方法 findAll

User user2 = new User();
user2.setUsername("admin");
Example<User> example = Example.of(user2);
List<User> one = userRepository.findAll(example, Sort.by("username").descending());

QueryByExampleExecutor 接口方法 findOne

User user3 = new User();
user3.setId(1L);
Example<User> example1 = Example.of(user3);
Optional<User> user4 = userRepository.findOne(example1); 

QueryByExampleExecutor 接口方法 count

User user5 = new User();
user5.setId(1L);
Example<User> example2 = Example.of(user3); 

QueryByExampleExecutor 接口方法 findAll 模糊查找

User user6 = new User();
user6.setUsername("admin");
ExampleMatcher exampleMatcher = ExampleMatcher.matching().withMatcher("username", ExampleMatcher.GenericPropertyMatchers.startsWith());
Example<User> example3 = Example.of(user2,exampleMatcher);
List<User> one2 = userRepository.findAll(example3, Sort.by("username").descending());;

根据hql查询用户名

User admin = userRepository.findByHQL("admin");

根据sql查询用户名

User admin1 = userRepository.findBySQL("admin", "123456");

根据用户名和密码查询

User admin2 = userRepository.findByUsernameAndPassword("admin", "123456");

根据用户名查询

User admin3 = userRepository.findByUsername("admin");

jdbcTemplate查询

User user = jdbcTemplate.queryForObject("select id,username,password from user where id=?",new BeanPropertyRowMapper<>(User.class) , new Integer[]{1});
log.info("用户名为："+user.getUsername()+"\n"+"密码为："+user.getPassword());
//单个字段查询
User mUser = jdbcTemplate.queryForObject("select password from user where id=?",new BeanPropertyRowMapper<>(User.class) , new Integer[]{1});
log.info("密码为"+mUser.getPassword());
//多个用户查询 返回为list
List<User> users = jdbcTemplate.query("select * from user", new BeanPropertyRowMapper<>(User.class));
log.info("查询大小"+users.size());

多个用户查询 返回为map

List< Map<String, Object>> stringObjectMap = jdbcTemplate.queryForList("select id,username,password from user");
log.info("查询大小"+stringObjectMap.size());

单个用户查询 返回为map

Map<String, Object> map = jdbcTemplate.queryForMap("select * from user where id=?",new Integer[]{1});
log.info("用户名为："+map.get("username").toString()+"\t"+"密码为："+map.get("password").toString());
//返回表的一些信息
SqlRowSet sqlRowSet = jdbcTemplate.queryForRowSet("select * from user");
System.out.println(sqlRowSet.getMetaData().getColumnName(1));
System.out.println(sqlRowSet.getMetaData().getColumnClassName(1));
System.out.println(sqlRowSet.getMetaData().getColumnLabel(1));
System.out.println(sqlRowSet.getMetaData().getCatalogName(1));
System.out.println(sqlRowSet.getMetaData().getColumnType(1));
System.out.println(sqlRowSet.getMetaData().getColumnTypeName(1));
System.out.println(sqlRowSet.getMetaData().getPrecision(1));
System.out.println(sqlRowSet.getMetaData().getScale(1));
System.out.println(sqlRowSet.getMetaData().getColumnDisplaySize(1));
System.out.println(sqlRowSet.getMetaData().getSchemaName(1));
System.out.println(sqlRowSet.getMetaData().getTableName(1));
    while (sqlRowSet.next()){
        //第几行
        int row = sqlRowSet.getRow();
        System.out.println(row);
        System.out.println("id为："+sqlRowSet.getInt("id"));
        System.out.println("username为："+sqlRowSet.getString("username"));
        System.out.println("password为："+sqlRowSet.getString("password"));
    }