Servlet案例7:jsp技术及案例

jsp运行原理:

根据jsp文件创建java文件(servlet),并编译运行

第一次访问时会被翻译成servlet后执行

jsp三个指令:

1.page指令:页面翻译运行的属性的配置(通常使用默认)

language="java" 可以嵌入的语言

contentType="text/html; charset=UTF-8" 设置servlet的response.setContentType内容

pageEncoding="UTF-8" 当前jsp文件的编码

session="true" 默认session可以直接使用

import="java.util.*" 导入java包

errorPage="xxx.jsp" 如果java代码有错,跳转到某个新页面

注意这里的错误不是404错误,而是代码错误,如果要配置404错误跳转的页面,需要在web.xml中配置

Servlet案例7:jsp技术及案例

isErrorPage="true" 是否是由于错误跳转后的页面

2.include指令:可以将其他的jsp页面包含到另一个jsp页面中

<%@ include file ="地址" %>

3.taglib指令:在jsp页面中引入标签库

<%@taglib uri="标签库地址" prefix="前缀"%>

jsp内置对象:

需要特别强调的2个对象

1.out对象:作用:在客户端页面输出内容

三种方法:

1.<% out.write("hello world");%>

2.<% response.getWriter().write("hello world");%>

3.<%="hello world"%>

本质上后两者都是转化成out对象

1,3写入out缓冲区,2写入response缓冲区

由于tomcat会从response缓冲区获得内容,所以out缓冲区内容会被刷到response缓冲区

于是先输出的是2,但是设置缓冲区(默认8kb)buffer=0kb,则按顺序输出

2.pageContext对象:页面上下文对象

是一个域对象,范围是当前页面

域对象方法setAttribute等和request,session域类似

范围可以设置

//使用pageContext向request域存数据
        //request.setAttribute("name", "zhangsan");
        //pageContext.setAttribute("name", "sunba");
        //pageContext.setAttribute("name", "lisi", PageContext.REQUEST_SCOPE);//request域
        //pageContext.setAttribute("name", "wangwu", PageContext.SESSION_SCOPE);//session域
        //pageContext.setAttribute("name", "tianqi", PageContext.APPLICATION_SCOPE);//application域

取出

<%=request.getAttribute("name") %>
<%=pageContext.getAttribute("name", PageContext.REQUEST_SCOPE)%>

特有的方法:findAttribute

<!-- findAttribute会从小到大搜索域的范围中的name -->
<!-- page域<request域<session域<application域 -->
<%=pageContext.findAttribute("name") %>

获得其他对象

<%
        pageContext.getRequest();
        pageContext.getOut();
    %>

静态包含和动态包含:

静态:<%@include file="地址" %>

合成一个页面,再进行翻译成java文件

动态:<jsp:include page="地址"/>

两个jsp文件翻译成java文件,编译运行

运行阶段调用方法include

请求转发:

<jsp:forward page="资源"/>

转发后地址不变

接下来做一个案例:

动态显示商品列表

数据库准备:

Servlet案例7:jsp技术及案例Servlet案例7:jsp技术及案例
CREATE DATABASE web;
USE web;
CREATE TABLE `product` (
  `pid` VARCHAR(50) 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,
  PRIMARY KEY (`pid`)
)
View Code

添加多条数据,这里略

对应类:

Servlet案例7:jsp技术及案例Servlet案例7:jsp技术及案例
package domain;

public class Product {
    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;
    }
}
View Code

servlet:

Servlet案例7:jsp技术及案例Servlet案例7:jsp技术及案例
package servlet;

import java.io.IOException;
import java.sql.SQLException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;

import domain.Product;
import utils.DataSourceUtils;

public class ProductListServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //准备所有商品数据,存入List
        QueryRunner runner = new QueryRunner(DataSourceUtils.getDataSource());
        List<Product> productList = null;
        String sql = "select * from product";
        try {
            productList = runner.query(sql, new BeanListHandler<Product>(Product.class));
        } catch (SQLException e) {
            e.printStackTrace();
        }
        //将数据存到request域,转发给jsp文件
        request.setAttribute("productList", productList);
        request.getRequestDispatcher("/product_list.jsp").forward(request, response);
        
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}
View Code

用到的连接池工具类(注意c3p0-config.xml的配置):

Servlet案例7:jsp技术及案例Servlet案例7:jsp技术及案例
package utils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class DataSourceUtils {

    private static DataSource dataSource = new ComboPooledDataSource();

    private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();

    // 直接可以获取一个连接池
    public static DataSource getDataSource() {
        return dataSource;
    }

    // 获取连接对象
    public static Connection getConnection() throws SQLException {

        Connection con = tl.get();
        if (con == null) {
            con = dataSource.getConnection();
            tl.set(con);
        }
        return con;
    }

    // 开启事务
    public static void startTransaction() throws SQLException {
        Connection con = getConnection();
        if (con != null) {
            con.setAutoCommit(false);
        }
    }

    // 事务回滚
    public static void rollback() throws SQLException {
        Connection con = getConnection();
        if (con != null) {
            con.rollback();
        }
    }

    // 提交并且 关闭资源及从ThreadLocall中释放
    public static void commitAndRelease() throws SQLException {
        Connection con = getConnection();
        if (con != null) {
            con.commit(); // 事务提交
            con.close();// 关闭资源
            tl.remove();// 从线程绑定中移除
        }
    }

    // 关闭资源方法
    public static void closeConnection() throws SQLException {
        Connection con = getConnection();
        if (con != null) {
            con.close();
        }
    }

    public static void closeStatement(Statement st) throws SQLException {
        if (st != null) {
            st.close();
        }
    }

    public static void closeResultSet(ResultSet rs) throws SQLException {
        if (rs != null) {
            rs.close();
        }
    }

}
View Code

jsp页面中的内容:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="java.util.*" %>
<%@ page import="domain.*" %>
......
......
        <%
        
            
            //获得集合List<Product>
            List<Product> productList = (List<Product>)request.getAttribute("productList");
            if(productList!=null){
                for(Product product : productList){
                    out.write("<div class='col-md-2' style='height:250px'>");
                    out.write("<a href='product_info.htm'>");
                    out.write("<img src='"+product.getPimage()+"' width='170' height='170' style='display: inline-block;'>");
                    out.write("</a>");
                    out.write("<p><a href='product_info.html' style='color: green'>"+product.getPname()+"</a></p>");
                    out.write("<p><font color='#FF0000'>商城价:&yen;"+product.getShop_price()+"</font></p>");
                    out.write("</div>");
                }
            }
        
        
        %>

web.xml:

Servlet案例7:jsp技术及案例Servlet案例7:jsp技术及案例
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>WEB7</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <description></description>
    <display-name>ProductListServlet</display-name>
    <servlet-name>ProductListServlet</servlet-name>
    <servlet-class>servlet.ProductListServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ProductListServlet</servlet-name>
    <url-pattern>/productList</url-pattern>
  </servlet-mapping>
</web-app>
View Code

这里运用了简单的MVC三层架构

注意:访问/product_list.jsp将会没有内容

访问/productList查询数据库转发后才会有内容

相关推荐