关于对javaUtils封装和三层架构的笔记
1.什么是三层架构：
三层架构(3-tier architecture) 通常意义上的三层架构就是将整个业务应用划分为：界面层（user interface layer）、业务逻辑层（business logic layer）、数据访问层（data access layer）。区分层次的目的即为了“高内聚低耦合”的思想。在软件体系架构设计中，分层式结构是最常见，也是最重要的一种结构。微软推荐的分层式结构一般分为三层，从下至上分别为：数据访问层、业务逻辑层（又或称为领域层）、表示层。
2.三层架构的优点：
web层
1>接收数据：本案例不需要接收数据
2>用list接受查询结果（常用于收集查询结果集）
定义一个list集合productlist泛型为product用于接收service.findallproduct();的返回值。
3>传递数据
list<product> productlist =service.findallproduct();
service层
1>传递数据
return dao.findallcategory();
dao层
1>链接数据库queryrunner()的有参链接
queryrunner runner = new queryrunner(datasourceutils.getdatasource());
string sql = "select * from product";
list接受查询到的数据
list<product> productlist = runner.query(sql, new beanlisthandler<product>(product.class));
数据的回写
return productlist;
web层
将查询到被回写的数据放入request域中并转发到jsp中进行显示
request.setattribute("productlist", productlist);
request.getrequestdispatcher("/admin/product/list.jsp").forward(request, response);
3.关于数据的封装和回写
1>list<string>,list<user> map<string, string> map<string, user>的赋值和遍历
//1）遍历strlist<string>
list<string> strlist = new arraylist<string>();
strlist.add("一");
strlist.add("二");
strlist.add("三");
strlist.add("四");
request.setattribute("strlist", strlist);
//2）遍历list<user>的值
list<user> userlist = new arraylist<user>();
user user1 = new user();
user1.setid(1);
user1.setname("lisi");
user1.setpassword("1234");
userlist.add(user1);
user user2 = new user();
user2.setid(2);
user2.setname("wangwu");
user2.setpassword("123456");
userlist.add(user2);
request.setattribute("userlist", userlist);
//3）遍历map<string,string>的值
map<string, string> strmap = new hashmap<string, string>();
strmap.put("key1", "一");
strmap.put("key2", "二");
strmap.put("key3", "三");
strmap.put("key4", "四");
request.setattribute("strmap", strmap);
//4）遍历map<string,user>的值
map<string, user> usermap = new hashmap<string, user>();
usermap.put("key1", user1);
usermap.put("key2",user2);
request.setattribute("usermap", usermap);
遍历(jstl)
<h1>取出strlist数据</h1>
<c:foreach items="${strlist}" var="str">
${str}<br>
</c:foreach>
<h1>取出userlist数据</h1>
<c:foreach items="${userlist}" var="user">
${user.id}<br>
${user.name}<br>
${user.password}<br>
</c:foreach>
<h1>取出strmap数据</h1>
<c:foreach items="${strmap}" var="strmap">
${strmap.key}=${strmap.value}<br>
</c:foreach>
<h1>取出usermap数据</h1>
<c:foreach items="${usermap}" var="usermap">
${usermap.key }=${usermap.value.name}=${usermap.value.password}<br>
</c:foreach>
2>map<string,string>封装数据
map<string, string[]> properties = request.getparametermap();
product product = new product();
try {
//将properties中的数据封装到product对象中
beanutils.populate(product, properties);
} catch (illegalaccessexception | invocationtargetexception e) {
// todo auto-generated catch block
e.printstacktrace();
}
3>手动的封装product中自己想要的数据
product.setpimage("products/1/c_0033.jpg");
domain：product
package com.hdh.domain;
public class product {
// `pid` varchar(32) not null,
// `pname` varchar(50) default null,
// `market_price` double default null,
// `shop_price` double default null,
// `pimage` varchar(200) default null,
// `pdate` date default null,
// `is_hot` int(11) default null,
// `pdesc` varchar(255) default null,
// `pflag` int(11) default null,
// `cid` varchar(32) default null,
private string pid;
private string pname;
private double market_price;
private double shop_price;
private string pimage;
private string pdate;
private int is_hot;
private string pdesc;
private int pflag;
private string cid;
public string getpid() {
return pid;
}
public void setpid(string pid) {
this.pid = pid;
}
public string getpname() {
return pname;
}
public void setpname(string pname) {
this.pname = pname;
}
public double getmarket_price() {
return market_price;
}
public void setmarket_price(double market_price) {
this.market_price = market_price;
}
public double getshop_price() {
return shop_price;
}
public void setshop_price(double shop_price) {
this.shop_price = shop_price;
}
public string getpimage() {
return pimage;
}
public void setpimage(string pimage) {
this.pimage = pimage;
}
public string getpdate() {
return pdate;
}
public void setpdate(string pdate) {
this.pdate = pdate;
}
public int getis_hot() {
return is_hot;
}
public void setis_hot(int is_hot) {
this.is_hot = is_hot;
}
public string getpdesc() {
return pdesc;
}
public void setpdesc(string pdesc) {
this.pdesc = pdesc;
}
public int getpflag() {
return pflag;
}
public void setpflag(int pflag) {
this.pflag = pflag;
}
public string getcid() {
return cid;
}
public void setcid(string cid) {
this.cid = cid;
}
}