javaweb——三层架构
目录
三层架构
软件分层模式
1.为什么需要分层
2.软件设计中的分层模式
3.分层
4.三层架构：表示层、业务逻辑层、数据访问层
5.分层的实现
三层架构
软件分层模式
1.为什么需要分层
业务处理的代码与JSP代码混在一起，不易于阅读，不易于代码维护，采用三层软件设计架构后，软件系统在可扩展性和可复用性方面得到极大提高。
2.软件设计中的分层模式
分层模式是最常见的一种架构模式；甚至可以说分层模式是很多架构模式的基础。
3.分层
①分层模式是将解决方案的组件分隔不同的层中（分工合作，细化）
②每一层的组件应保持内聚性（部门之间常联系）
③每一层都应与其下面的各层保持松耦合
4.三层架构：表示层、业务逻辑层、数据访问层
①表示层：位于最外层 ( 最上层 )，使用户能够直接访问，用于显示数据和接收用户输入的数据，为用户提供一种交互式操作界面。在 Web 应用程 序中，表示层一般以 JSP 文件、HTML文件为主；
②业务逻辑层：其主要功能是提供对业务逻辑处理的封装，在业务逻辑层中，通常会定义些接口，表示层通过调用业务逻辑层的接口实现各种操作， 如数据有效性的检验. 业务辑描述等相关功能，业务逻辑层经常放在 service 包或 biz 包下，btz 是英文 buslness 的缩写，意思是 '业务逻 辑"；
③数据访问层：该层实现对数据的保存和读取操作。数据访问，可以访问关系数椐库、文件或 XML 文档等。数据访问层通常放在 dao 包下，DAO 是 英文 Data Access Object 的缩写，意思是 "数据访问对象 "；
5.分层的实现
1.显示层：JSP HTML，css ,JS,do处理页面
2.业务逻辑层
services|biz 从数据访问层拿到数据后进行相关判断逻辑处理。
简单业务逻辑层：直接从数据访问层拿到数据进行操作即可。
复杂业务逻辑层：
从数据访问层拿到数据后，做筛选
比如：删除 从数据访问层拿到对应的数据进行判断，看删除的数据是否在表中存在
如果存在，再调用删除的方法删除即可。
oracle事务处理。 （当实现一个功能时，需要满足2个条件以上，事务处理的机制：要么一起成功，要么一起失败）
银行转账
3.数据访问层
dao(接口+实现类)，utils
从DB中获取数据 增删改查
4.通过实体将三个层进行联系起来。
实体不属于三层
特点：
高内聚 低耦合高内聚：功能内部的代码非常严谨
低耦合：功能与功能之间依赖性很小，一个功能出问题不会影响其它功能的运行，俗称：模块化。
案例：简单步骤
dao类——数据访问层
package com.zking.news.dao.impl;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import com.zking.news.dao.INewsDao;
import com.zking.news.entity.News;
import com.zking.news.entity.Theme;
import com.zking.news.utils.DBHelper;
public class NewsDaoImpl implements INewsDao {
@Override
public List queryNewsAll() {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
List list = new ArrayList();
try {
conn = DBHelper.getConn();
String sql = "select * from tb_news";
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
// 获取分类编号rs.getInt("ntid");
Theme theme = new ThemeDaoImpl().getThemeByTid(rs.getInt("ntid"));
list.add(new News(rs.getInt("nid"), theme, rs.getString("ntitle"), rs.getString("nauthor"),
rs.getString("nsummary"), rs.getString("ncontent"), rs.getString("nimage"),
rs.getString("ndate"), rs.getInt("ncount")));
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBHelper.myClose(conn, ps, rs);
}
return list;
}
@Override
public List queryNewsAll2() {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
List list = new ArrayList();
try {
conn = DBHelper.getConn();
String sql = "select b.* from ( select a.*,rownum as rid from tb_news a ) b where b.rid between 1 and 5";
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
// 获取分类编号rs.getInt("ntid");
Theme theme = new ThemeDaoImpl().getThemeByTid(rs.getInt("ntid"));
list.add(new News(rs.getInt("nid"), theme, rs.getString("ntitle"), rs.getString("nauthor"),
rs.getString("nsummary"), rs.getString("ncontent"), rs.getString("nimage"),
rs.getString("ndate"), rs.getInt("ncount")));
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBHelper.myClose(conn, ps, rs);
}
return list;
}
@Override
public List queryNewsAll3(int pageIndex, int pageSize) {
// 1 5 第一页 5条数据 start = 1 end = 5;
// 2 5 第二页 5条数据 start = 6 end = 10
// 根据参数pageIndex和pageSize来计算区间查询的规律
int start = (pageIndex - 1) * pageSize + 1;
int end = pageIndex * pageSize;
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
List list = new ArrayList();
try {
conn = DBHelper.getConn();
String sql = "select b.* from ( select a.*,rownum as rid from tb_news a ) b where b.rid between " + start
+ " and " + end + "";
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
// 获取分类编号rs.getInt("ntid");
Theme theme = new ThemeDaoImpl().getThemeByTid(rs.getInt("ntid"));
list.add(new News(rs.getInt("nid"), theme, rs.getString("ntitle"), rs.getString("nauthor"),
rs.getString("nsummary"), rs.getString("ncontent"), rs.getString("nimage"),
rs.getString("ndate"), rs.getInt("ncount")));
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBHelper.myClose(conn, ps, rs);
}
return list;
}
@Override
public List queryNewsAll4(String strName) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
List list = new ArrayList();
try {
conn = DBHelper.getConn();
String sql = "select * from tb_news where ntitle like '%" + strName + "%'";
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
// 获取分类编号rs.getInt("ntid");
Theme theme = new ThemeDaoImpl().getThemeByTid(rs.getInt("ntid"));
list.add(new News(rs.getInt("nid"), theme, rs.getString("ntitle"), rs.getString("nauthor"),
rs.getString("nsummary"), rs.getString("ncontent"), rs.getString("nimage"),
rs.getString("ndate"), rs.getInt("ncount")));
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBHelper.myClose(conn, ps, rs);
}
return list;
}
@Override
public List queryNewsAll5(int pageIndex, int pageSize, String strName) {
// 1 5 第一页 5条数据 start = 1 end = 5;
// 2 5 第二页 5条数据 start = 6 end = 10
// 根据参数pageIndex和pageSize来计算区间查询的规律
int start = (pageIndex - 1) * pageSize + 1;
int end = pageIndex * pageSize;
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
List list = new ArrayList();
try {
conn = DBHelper.getConn();
String sql = "select b.* from (\r\n" + " select a.*,rownum as rid from (\r\n"
+ " select * from tb_news where ntitle like '%" + strName + "%'\r\n"
+ " )a\r\n" + ")b where b.rid between " + start + " and " + end + "";
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
// 获取分类编号rs.getInt("ntid");
Theme theme = new ThemeDaoImpl().getThemeByTid(rs.getInt("ntid"));
list.add(new News(rs.getInt("nid"), theme, rs.getString("ntitle"), rs.getString("nauthor"),
rs.getString("nsummary"), rs.getString("ncontent"), rs.getString("nimage"),
rs.getString("ndate"), rs.getInt("ncount")));
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBHelper.myClose(conn, ps, rs);
}
return list;
}
public List queryNewsAll5(int pageIndex, int pageSize, String strName, int ntid) {
int start = (pageIndex - 1) * pageSize + 1;
int end = pageIndex * pageSize;
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
List list = new ArrayList();
try {
conn = DBHelper.getConn();
// 默认根据标题进行模糊查询 如果没有点击搜索 默认将strName = ""
String sql = "select * from tb_news where ntitle like '%" + strName + "%' ";
// 当点击了主题分类时 将点击的分类编号作为条件拼接到模糊查询的后面
if (ntid != 0) {
sql += " and ntid = " + ntid;
}
// System.out.println(sql);
// 进行分页
sql = " select b.* from ( select a.*,rownum as rid from ( " + sql + " ) a ) b where b.rid between " + start
+ " and " + end + "";
System.out.println(sql);
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
// 获取分类编号rs.getInt("ntid");
Theme theme = new ThemeDaoImpl().getThemeByTid(rs.getInt("ntid"));
list.add(new News(rs.getInt("nid"), theme, rs.getString("ntitle"), rs.getString("nauthor"),
rs.getString("nsummary"), rs.getString("ncontent"), rs.getString("nimage"),
rs.getString("ndate"), rs.getInt("ncount")));
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBHelper.myClose(conn, ps, rs);
}
return list;
}
public static void main(String[] args) {
// List queryNewsAll5 = new NewsDaoImpl().queryNewsAll5(1, 4, "1", 1);
// for (News news : queryNewsAll5) {
// System.out.println(news.getNtitle());
// }
//System.out.println(new NewsDaoImpl().queryNewsAll6(1, 5, 0).size());
// List list = new NewsDaoImpl().queryNewsAll6(1, 5, 6);
// for (News news : list) {
// System.out.println(news.getNtitle());
// }
System.out.println(new NewsDaoImpl().getNewsCountByNtid(6));
}
@Override
public int getNewsCount() {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
int count = 0;// 保存表的总记录数
try {
conn = DBHelper.getConn();
String sql = "select count(*) from tb_news";
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
if (rs.next()) {
count = rs.getInt(1);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBHelper.myClose(conn, ps, rs);
}
return count;
}
@Override
public int getNewsCount(String strName) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
int count = 0;// 保存表的总记录数
try {
conn = DBHelper.getConn();
String sql = "select count(*) from tb_news where ntitle like '%" + strName + "%'";
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
if (rs.next()) {
count = rs.getInt(1);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBHelper.myClose(conn, ps, rs);
}
return count;
}
// }
//
// }
@Override
public List queryNewsAll6(int pageIndex, int pageSize, int ntid) {
int start = (pageIndex - 1) * pageSize + 1;
int end = pageIndex * pageSize;
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
List list = new ArrayList();
String sql = "";
String sqlNtid = "";
try {
conn = DBHelper.getConn();
if(ntid!=0) {
sqlNtid = " where ntid = "+ntid;
}
sql = "select c.* from ( select b.*,rownum as rid from (select * from tb_news "+sqlNtid+")b)c where c.rid between "+start+" and "+end+"";
/*
if(ntid == 0) {
sql = "select b.* from\r\n" +
"(\r\n" +
"select a.*,rownum as rid from tb_news a\r\n" +
") b where b.rid between "+start+" and "+end+"";
}else {
sql = "select c.* from \r\n" +
"(\r\n" +
"select b.*,rownum as rid from (\r\n" +
" select * from tb_news where ntid = "+ntid+" \r\n" +
")b\r\n" +
"\r\n" +
")c where c.rid between "+start+" and "+end+"";
}*/
System.out.println(sql);
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
// 获取分类编号rs.getInt("ntid");
Theme theme = new ThemeDaoImpl().getThemeByTid(rs.getInt("ntid"));
list.add(new News(rs.getInt("nid"), theme, rs.getString("ntitle"), rs.getString("nauthor"),
rs.getString("nsummary"), rs.getString("ncontent"), rs.getString("nimage"),
rs.getString("ndate"), rs.getInt("ncount")));
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBHelper.myClose(conn, ps, rs);
}
return list;
}
@Override
public int getNewsCountByNtid(int ntid) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
int count = 0;// 保存表的总记录数
try {
conn = DBHelper.getConn();
String sql = "select count(*) from tb_news ";
if(ntid!=0) {
sql+=" where ntid = "+ntid;
}
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
if (rs.next()) {
count = rs.getInt(1);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBHelper.myClose(conn, ps, rs);
}
return count;
}
@Override
public List queryNewsAll7(int pageIndex, int pageSize, String strName, int ntid) {
int start = (pageIndex - 1) * pageSize + 1;
int end = pageIndex * pageSize;
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
List list = new ArrayList();
try {
conn = DBHelper.getConn();
// 默认根据标题进行模糊查询 如果没有点击搜索 默认将strName = ""
String sql = "select * from tb_news where ntitle like '%" + strName + "%' ";
// 当点击了主题分类时 将点击的分类编号作为条件拼接到模糊查询的后面
if (ntid != 0) {
sql += " and ntid = " + ntid;
}
// System.out.println(sql);
// 进行分页
sql = " select b.* from ( select a.*,rownum as rid from ( " + sql + " ) a ) b where b.rid between " + start
+ " and " + end + "";
System.out.println(sql);
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
// 获取分类编号rs.getInt("ntid");
Theme theme = new ThemeDaoImpl().getThemeByTid(rs.getInt("ntid"));
list.add(new News(rs.getInt("nid"), theme, rs.getString("ntitle"), rs.getString("nauthor"),
rs.getString("nsummary"), rs.getString("ncontent"), rs.getString("nimage"),
rs.getString("ndate"), rs.getInt("ncount")));
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBHelper.myClose(conn, ps, rs);
}
return list;
}
@Override
public int getNewsCountByMoHuTid(String strName, int ntid) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
int count = 0;// 保存表的总记录数
try {
conn = DBHelper.getConn();
String sql = "select count(*) from tb_news where ntitle like '%" + strName + "%' and ntid = "+ntid;
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
if (rs.next()) {
count = rs.getInt(1);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBHelper.myClose(conn, ps, rs);
}
return count;
}
}
biz类——业务逻辑层
package com.zking.news.biz.impl;
import java.util.List;
import com.zking.news.biz.INewsBiz;
import com.zking.news.dao.INewsDao;
import com.zking.news.dao.impl.NewsDaoImpl;
import com.zking.news.entity.News;
/**
*
* @author Administrator
* 实现新闻，（业务逻辑层）
*/
public class NewsBizImpl implements INewsBiz{
INewsDao ind = new NewsDaoImpl();
@Override
public List queryNewsAll5(int pageIndex, int pageSize, String strName, int ntid) {
return ind.queryNewsAll7(pageIndex, pageSize, strName, ntid);
}
@Override
public int getNewsCount(String strName, int ntid) {
return ind.getNewsCountByMoHuTid(strName, ntid);
}
}
实现区域——显示层
- 全部
<%
//实例化分类DAO
IThemeDao itd = new ThemeDaoImpl();
//调用查询所有分类的dao方法
List
listThemes = itd.queryThemeAll();
for(Theme theme:listThemes){
%>
<%=theme.getTname() %>
<%
}
%>
<%
//当点击了主题分类时 跳转本页面 获取tid
//没有点击主题分类 不需要获取
String id = request.getParameter("tid");//null
int tid = 0;//保存最终的编号
if(id!=null){
tid = Integer.valueOf(id);
}
System.out.println("tid = "+tid);
//手动点击了搜索提交按钮 获取到模糊查询的关键字 否则没有点击的情况下 null 转换
String strName = request.getParameter("strName");
if(strName==null){//没有手动点击搜索
strName="";
}
//实例化DAO
INewsBiz inb = new NewsBizImpl();
//定义变量存储页码以及每一夜显示的数据
int pageIndex = 1;
int pageSize = 5;
int pageMax = 0;//存储最大页码
//当点击分页区域的下一页超链接时，获取这个参数
String pIndex = request.getParameter("pageIndex");
//判断，只有你点击了下一页 才将pIndex赋值给pageIndex
if(null!=pIndex){//不为空 说明点击了
pageIndex = Integer.valueOf(pIndex);
}
//根据dao求出总记录数
int count = inb.getNewsCount(strName, tid);
pageMax = count%pageSize==0?count/pageSize:count/pageSize+1;
System.out.println("最大页码: "+pageMax);
//调用查询所有新闻的方法
List listNews = inb.queryNewsAll5(pageIndex, pageSize, strName, tid);
for(News news:listNews){
%>
- <%=news.getNtitle() %> <%=news.getNdate() %>
<%
}
%>