Java 连接数据库的几种方法

1.使用@Query 注释

public interface BookRepository extends JpaRepository<Book, Long>{    @Query(value = "SELECT * FROM book WHERE name = ?1 AND borrowedAt IS NULL AND createdAt > ?2", nativeQuery = ture)    List<Book> numsRes(String userName, Date rangeDate);}

2.使用 JPAQuery

import com.mysema.query.types.Predicate@PersistenceContext(unitName = "book")private EntityManager entityManager;QBook BOOK = QBook.book;private static final Expression<?>[] BOOK_FIELD = {    BOOK.name,    BOOK.id};private Predicate makePredicate(String userName, Date createdAt){    BooleanExpression predicate = null;    List<BooleanExpression> ps = new ArrayList<>();    if(userName != null){    ps.add(BOOK.userName).eq(userName);    }    if(createdAt != null){    ps.add(BOOK.creaedAt).goe(createdAt);    }    if(!ps.isEmpty()){        predicate = ps.get(0);        if(ps.size() == 2){            predicate.and(ps.get(1));        }    }    return predicate;}private JPAQuery getQueryForBook(Predicate predicate, int startRow, int pageSize){    Epression sortfield = BOOK.createdAt;    OrderSpecifier orderSpecifier = new OrderSpecifier(Order.ASC, sortfield);    JPAQuery jpaQuery = new JPAQUERY(entityManager);    jpaQuery.from(BOOK)    .where(predicate)    .orderBy(sortfield)    .offset(startRow)    .limit(pageSize);    return jpaQuery;}private List<BookResult> getBook(Predicate predicate, int startRow, int pageSize){    List<BookResult> list = new ArrayList<>();    JPAQuery jpaQuery = getQueryForBook(predicate, startRow, pageSize);    final List<Tuple> results = jpaQuery.list(BOOK_FIELD);    for(Tuple tuple:results){        list.add(wrapForBook(tuple));    }    return list;}private BookResult wrapForBook(Tuple tuple){    BookResult bookResult = new BookResult();    bookResult.setName(tuple.get(BOOK.name));    bookResult.setId(tuple.get(BOOK.id));    return bookResult;}

3.使用 Jdbctemplate

Jdbctemplate bookTemplate;private static final String SQL = "SELECT * FROM book WHERE name = :name"public List<BookResult> findBook(String name){    Map<String, Object> params = new HashMap<>();    params.put("name", name);    return bookTemplate.query(SQL, params, new RowMapper<Book>(){        @Override        public BookResult mapRow(ResultSet rs, int rowNum) throws SQLException{            BookResult bookResult = new BookResult();            bookResult.setid(rs.getLong("id"));            return bookResult;        }    });}