Java分页查询操作的两种实现办法

Dao实现类

public Listpage(int start, int end) {

String pagesql = "select * from (select id,name,price,descri,rownumrn from t_product)where rn between ? and ?";

List list = new ArrayList();

Product p = null;

Connection conn = null;

PreparedStatementstm = null;

ResultSetrs = null;

try {

conn = JDBCUtil.getConnection();

stm = conn.prepareStatement(pagesql);

stm.setInt(1, start);

stm.setInt(2, end);

rs = stm.executeQuery();

while (rs.next()) {

p = new Product(rs.getInt(1), rs.getString(2), rs.getDouble(3),

rs.getString(4));

list.add(p);

}

} catch (Exception e) {

thrownew RuntimeException("查询page全部异常", e);

} finally {

JDBCUtil.close(rs, stm, null);

}

return list;

}

public Long count() {

Connection conn = null;

PreparedStatementstm = null;

ResultSetrs = null;

Long count = null;

try {

conn = JDBCUtil.getConnection();

stm = conn.prepareStatement("select count(*) from t_product");

rs = stm.executeQuery();

while (rs.next()) {

count = rs.getLong(1);

}

} catch (Exception e) {

thrownew RuntimeException("查询count", e);

} finally {

JDBCUtil.close(rs, stm, null);

}

return count;

}

Service实现类

public PageBeanqueryPage(int pageNum, int pageSize) {

int start = (pageNum - 1) * pageSize + 1;

int end = pageNum * pageSize;

ProductDaodao = new ProductDaoImpl();

List page = dao.page(start, end);

Long sum = dao.count();

PageBeanpageBean = new PageBean();

pageBean.setCount(sum);

pageBean.setList(page);

pageBean.setPageNum(pageNum);

pageBean.setPageSize(pageSize);

return pageBean;

}

Entity实体类

publicclass PageBean {

private Integer pageNum;

private Integer pageSize;

private Long count;

private Listlist;

public PageBean() {

}

public PageBean(Integer pageNum, Integer pageSize, Long count, List list) {

this.pageNum = pageNum;

this.pageSize = pageSize;

this.count = count;

this.list = list;

}

public Integer getPageNum() {

return pageNum;

}

publicvoid setPageNum(Integer pageNum) {

this.pageNum = pageNum;

}

public Integer getPageSize() {

return pageSize;

}

publicvoid setPageSize(Integer pageSize) {

this.pageSize = pageSize;

}

public Long getCount() {

return count;

}

publicvoid setCount(Long count) {

this.count = count;

}

public ListgetList() {

return list;

}

publicvoid setList(List list) {

this.list = list;

}

}

Action实现类

private PageBeanpageBean;

public PageBeangetPageBean() {

return pageBean;

}

publicvoid setPageBean(PageBeanpageBean) {

this.pageBean = pageBean;

}

public ListgetProducts() {

return products;

}

publicvoid setProducts(List products) {

this.products = products;

}

private Listproducts;

public String queryAll() {

ProductService service = new ProductServiceImpl();

try {

// List list = service.queryAllProduct();

PageBean list = service.queryPage(1, 10);

pageBean = list;

setProducts(list.getList());

// ServletActionContext.getRequest().setAttribute("products", list);

// session.put("products", list);

return"queryall";

} catch (Exception e) {

// TODO Auto-generated catch block

session.put("emass", "查询全部出错");

return"LOGIN";

}

}

public String page() {

ProductService service = new ProductServiceImpl();

PageBean bean = service.queryPage(pageBean.getPageNum(), pageBean.getPageSize());

pageBean = bean;

products = bean.getList();

return"queryall";

}

Struts2.xml

/product/ShowAllProducts.jsp

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