不会框架不要紧，我带你自定义框架

前言：这标题说的有点大了，当一回标题党，之前在学JSP的时候提到了JSTL和EL表达式，由于一直钟情于Servlet,迟迟没有更新别的，这回算是跳出来了。这回放个大招，用Spring+SpringMVC+Spring Jdbc Template，实现一个增删改查加分页，但重点不在这，我的重心在于JSTL和EL表达式，标题虽然有点大，但话糙理不糙，我真的是要自定义框架，当然，这个框架可大可小，大的我不敢说，用JSTL自定义标签封装个分页还是可以的，也算补上JSTL和EL表达式的学习吧。对于那些一直跟着我跟新博客脚步的朋友，我提醒你们不要着急，你要是好奇就可以先试着跟着我的案例试试手，不要看到SSM框架就说还没学，不会啥的，哈哈，开玩笑，都没学怎么可能会呢，我说了，这篇的重点在于JSTL和EL表达式，重要的话说了不下三遍了，至于附加的SSM，我会持续跟新，会手把手带你理解的，别急，别急，就当先认识一下SSM吧。

环境准备

我用的开发工具是IDEA，如果有不会用IDEA的朋友可以看之前写过的博客《IDEA新手使用教程》，我建的这是一个Maven项目，如果有朋友不知道Maven，可以先看一下我之前写的介绍Maven的博客《Maven》,不知道如何配置Maven环境的可以看《Maven的安装与配置》https://www.cnblogs.com/zyx110/p/10801666.html不知道如何在IDEA中建Maven项目的朋友可以看《IDEA为新手专业打造》，此案例还会用到Tomcat,同样，不会在IDEA中配置Tomcat的朋友可以看《IDEA为新手专业打造》，好，完成这些，就可以开始敲代码了。

用JSTL封装框架

写之前先简单介绍一下JSTL和EL表达式：

JSTL简介及环境搭建

什么是JSTL

JSTL是Java中的一个定制标记库集

为什么要使用JSTL

实现了JSP页面中的代码复用，基于标签库原理，重复率较高的代码块支持复用，提高效率

书写JSP页面时可读性更强，长得很像XML，方便前端查看和参与开发

举例：

不同角色用户登录时显示不同提示信息

需要导入的JSTL模块

<!-- https://mvnrepository.com/artifact/javax.servlet/jstl -->
<dependency><groupId>javax.servlet</groupId><artifactId>jstl</artifactId><version>1.2</version>
</dependency>

EL表达式配合使用JSTL

第一个JSTL小程序

在JSP页面中导入JSTL标签库

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

使用out标签输出

<c:out value="Hello JSTL"></c:out>

JSTL标签的四大分类：核心标签、格式化标签、SQL标签、XML标签EL表达式

EL表达式全名为Expression Language，经常与JSTL配合使用，使得JSP页面更直观，写法更简单。

普通表达式的写法： <%=session.getValue("name") %>

EL表达式写法： <c:out value="${sessionScope.name}" />

EL表达式的格式

用美元符号“$”定界，内容包括在花括号“{ }”中；

"."与"[ ]"运算符

² 通常情况是通用的${user.sex}或${user["sex"]}

² "[ ]"还可以用来进行集合元素中的定位${booklist[0].price}

² 当包含特殊字符时，必须使用"[ ]"，例如：${user["first-name"]}

² 通过变量动态取值：${user[param]}，例如：param可以是name/sex/others

EL变量

EL自动类型转换

EL隐式对象

EL运算符

JSP自定义标签

什么是自定义标签

在实际开发过程中不能出现大量的html+java代码相混合的jsp页面，但是有时候jsp标签和第三方标签满足不了正常的开发工作，这就需要开发人员将业务逻辑封装到符合jsp规范的类或接口中，来自己定义标签从而满足不同的开发需求。这样做的缺点是会加重开发的工作量，但在开发过程中简化了前后端的沟通，便于后期的维护，这点工作量也是微不足道的。我们可以自己定义一套标签机制，让完全不懂写代码的人开发一套网站出来。

开发第一个自定义标签

案例场景：

在页面中显示当前时间，格式：“当前时间为：2017年8月1日 10:30:50”

如果使用传统的jsp脚本开发，代码如下：

<%SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");String date = sdf.format(new Date());%>当前时间为：<%=date %>

显示结果：

下面使用自定义标签库来实现这个案例

第一步：编写自定义标签的业务逻辑处理类

DateTag

package utils;import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;public class DateTag extends TagSupport {private String format="yyyy-MM-dd HH:mm:ss";private String color="blue";private String fontSize="12px";public void setFormat(String format) {this.format = format;}public void setColor(String color) {this.color = color;}public void setFontSize(String fontSize) {this.fontSize = fontSize;}public int doStartTag() throws JspException {//自定义业务SimpleDateFormat simpleDateFormat = new SimpleDateFormat(format);String date = simpleDateFormat.format(new Date());String htmlshow = "<p class='' style='font-size:"+fontSize+";color:"+color+"'>"+date+"</p>";try {pageContext.getOut().print(htmlshow);} catch (IOException e) {e.printStackTrace();}return super.doStartTag();}
}

第二步：在WEB-INF目录下编写*.tld文件注册标签

格式模板

datetag.tld

<?xml version="1.0" encoding="utf-8"?><taglib xmlns="http://java.sun.com/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"version="2.1"><tlib-version>1.0</tlib-version><short-name>myshortname</short-name><uri>http://mycompany.com</uri><tag><name>date</name><tag-class>utils.DateTag</tag-class><body-content>empty</body-content><attribute><name>format</name><required>false</required></attribute><attribute><name>color</name><required>false</required></attribute><attribute><name>fontSize</name><required>false</required></attribute></tag></taglib>

JSP显示

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<%@ taglib prefix="z" uri="http://mycompany.com" %>
<%@ taglib prefix="c" uri="http://mycompany.com" %>
<html>
<head><title>显示时间</title>
</head>
<body>
<h1>index.jsp</h1>
<c:date/>
</body>
</html>

Spring+SpringMVC+Spring Jdbc Template

数据库结构

项目结构

Pom.xml

<dependencies><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.11</version><scope>test</scope></dependency><!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api --><dependency><groupId>javax.servlet</groupId><artifactId>javax.servlet-api</artifactId><version>3.1.0</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.38</version></dependency><dependency><groupId>javax.servlet</groupId><artifactId>jstl</artifactId><version>1.2</version></dependency><!--Spring核心基础依赖--><dependency><groupId>org.springframework</groupId><artifactId>spring-core</artifactId><version>5.0.2.RELEASE</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-context</artifactId><version>5.0.2.RELEASE</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-beans</artifactId><version>5.0.2.RELEASE</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-expression</artifactId><version>5.0.2.RELEASE</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-aop</artifactId><version>5.0.2.RELEASE</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-jdbc</artifactId><version>5.0.2.RELEASE</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-tx</artifactId><version>5.0.2.RELEASE</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-web</artifactId><version>5.0.2.RELEASE</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>5.0.2.RELEASE</version></dependency><!--日志相关--><dependency><groupId>commons-logging</groupId><artifactId>commons-logging</artifactId><version>1.2</version></dependency>
</dependencies>

Web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app><servlet><servlet-name>springmvc</servlet-name><servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><load-on-startup>1</load-on-startup><init-param><param-name>contextConfigLocation</param-name><param-value>classpath:applicationContext.xml</param-value></init-param></servlet><servlet-mapping><servlet-name>springmvc</servlet-name><url-pattern>/</url-pattern></servlet-mapping><!--处理中文乱码--><filter><filter-name>encodingFilter</filter-name><filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class><init-param><param-name>encoding</param-name><param-value>UTF-8</param-value></init-param><init-param><param-name>forceEncoding</param-name><param-value>true</param-value></init-param></filter><filter-mapping><filter-name>encodingFilter</filter-name><url-pattern>/*</url-pattern></filter-mapping><!--设置访问静态资源--><servlet-mapping><servlet-name>default</servlet-name><url-pattern>*.css</url-pattern></servlet-mapping><servlet-mapping><servlet-name>default</servlet-name><url-pattern>*.js</url-pattern></servlet-mapping><servlet-mapping><servlet-name>default</servlet-name><url-pattern>*.jpg</url-pattern></servlet-mapping><servlet-mapping><servlet-name>default</servlet-name><url-pattern>*.png</url-pattern></servlet-mapping><servlet-mapping><servlet-name>default</servlet-name><url-pattern>*.gif</url-pattern></servlet-mapping><servlet-mapping><servlet-name>default</servlet-name><url-pattern>*.mp3</url-pattern></servlet-mapping><servlet-mapping><servlet-name>default</servlet-name><url-pattern>*.mp4</url-pattern></servlet-mapping></web-app>

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:context="http://www.springframework.org/schema/context"xmlns:tx="http://www.springframework.org/schema/tx"xmlns:mvc="http://www.springframework.org/schema/mvc"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsdhttp://www.springframework.org/schema/txhttp://www.springframework.org/schema/tx/spring-tx.xsdhttp://www.springframework.org/schema/mvchttp://www.springframework.org/schema/mvc/spring-mvc.xsd"><!--配置注解要扫描的包--><context:component-scan base-package="controller"></context:component-scan><context:component-scan base-package="dao"></context:component-scan><context:component-scan base-package="Service"></context:component-scan><context:component-scan base-package="pojo"></context:component-scan><context:component-scan base-package="utils"></context:component-scan><context:component-scan base-package="test"></context:component-scan><mvc:annotation-driven></mvc:annotation-driven><!--配置spring-jdbcTemplate--><bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"><property name="driverClassName" value="com.mysql.jdbc.Driver"></property><property name="url" value="jdbc:mysql://localhost:3306/bbb?useUnicode=true&characterEncoding=UTF-8"></property><property name="username" value="root"></property><property name="password" value="root"></property></bean><bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate"><property name="dataSource" ref="dataSource"></property></bean><!--配置事务--><bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"><property name="dataSource" ref="dataSource"></property></bean><!--注册事务注解驱动--><tx:annotation-driven transaction-manager="txManager"></tx:annotation-driven><!--配置访问静态资源--><mvc:resources mapping="/js/**" location="/js/"></mvc:resources><mvc:resources mapping="/css/**" location="/css/"></mvc:resources><mvc:resources mapping="/img/**" location="/img/"></mvc:resources><!--配置视图解析器--><bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"><!--配置前缀--><property name="prefix" value="/"></property><!--配置后缀--><property name="suffix" value=".jsp"></property></bean><!--创建文件上传组件对象--><bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"></bean>
</beans>

Book

package pojo;public class Book {@Overridepublic String toString() {return "Book{" +"id=" + id +", bookname='" + bookname + '\'' +", price=" + price +'}';}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getBookname() {return bookname;}public void setBookname(String bookname) {this.bookname = bookname;}public int getPrice() {return price;}public void setPrice(int price) {this.price = price;}private int id;private String bookname;private int price;}

PageBean

package pojo;import java.util.List;public class PageBean<T> {private int pageCode;//当前页码private int totalPage;//总页数private int count;//总记录数private int pageSize;//每页记录数private List<T> pageList;//每页的数据public PageBean(int pageCode, int pageSize, int count, List<T> pageList) {this.pageCode = pageCode;this.count = count;this.pageSize = pageSize;this.pageList = pageList;}public PageBean() {}public int getPageCode() {return pageCode;}public void setPageCode(int pageCode) {this.pageCode = pageCode;}public int getTotalPage() {int tp = count/pageSize;return count%pageSize==0 ? tp : tp+1;}public int getCount() {return count;}public void setCount(int count) {this.count = count;}public int getPageSize() {return pageSize;}public void setPageSize(int pageSize) {this.pageSize = pageSize;}public List<T> getPageList() {return pageList;}public void setPageList(List<T> pageList) {this.pageList = pageList;}
}

BookDao

package dao;import pojo.Book;import java.util.List;public interface BookDao {public List<Book> findByPage(int pageCode,int pageSize);public int count();
}

BookDaoImpl

package dao;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;
import pojo.Book;import java.util.List;
@Repository
public class BookDaoImpl implements BookDao {@Autowiredprivate JdbcTemplate jdbcTemplate;@Overridepublic List<Book> findByPage(int pageCode, int pageSize) {String sql = "select * from book limit ?,?";Object[] param = {(pageCode-1)*pageSize,pageSize};return jdbcTemplate.query(sql,new BeanPropertyRowMapper<Book>(Book.class),param);}@Overridepublic int count() {String sql = "select count(*) from book";return jdbcTemplate.queryForObject(sql,Integer.class);}
}

BookService

package Service;import pojo.Book;
import pojo.PageBean;public interface BookService {public PageBean<Book> findByPage(int pageCode,int pageSize);
}

BookServiceImpl

package Service;import dao.BookDao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import pojo.Book;
import pojo.PageBean;
@Service
public class BookServiceImpl implements BookService {@Autowiredprivate BookDao bookDao;@Overridepublic PageBean<Book> findByPage(int pageCode, int pageSize) {return new PageBean<Book>(pageCode,pageSize,bookDao.count(),bookDao.findByPage(pageCode,pageSize));}
}

BookController

package controller;import Service.BookService;
import com.sun.org.apache.xml.internal.resolver.readers.XCatalogReader;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import pojo.Book;
import pojo.PageBean;
import utils.RequestPage;@Controller
@RequestMapping("/book")
public class BookController {@Autowiredprivate BookService bookService;@RequestMapping("/query")public String findByPage(Integer page, Model model){page = RequestPage.getPage(page);//判断是否为空PageBean<Book> pageBean = bookService.findByPage(page,RequestPage.PAGE_SIZE);model.addAttribute("pageBean",pageBean);return "book";}}

DateTag

package utils;import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;public class DateTag extends TagSupport {private String format="yyyy-MM-dd HH:mm:ss";private String color="blue";private String fontSize="12px";public void setFormat(String format) {this.format = format;}public void setColor(String color) {this.color = color;}public void setFontSize(String fontSize) {this.fontSize = fontSize;}public int doStartTag() throws JspException {//自定义业务SimpleDateFormat simpleDateFormat = new SimpleDateFormat(format);String date = simpleDateFormat.format(new Date());String htmlshow = "<p class='' style='font-size:"+fontSize+";color:"+color+"'>"+date+"</p>";try {pageContext.getOut().print(htmlshow);} catch (IOException e) {e.printStackTrace();}return super.doStartTag();}
}

PageTag

package utils;import pojo.PageBean;import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
import java.io.IOException;public class PageTag extends TagSupport {private PageBean pageBean;private String url;public void setUrl(String url) {this.url = url;}public void setPageBean(PageBean pageBean) {this.pageBean = pageBean;}@Overridepublic int doStartTag() throws JspException {try {StringBuffer sb = new StringBuffer();//首页sb.append("<a href=\"" + url + "?page=1\">首页</a> ");//上一页if (pageBean.getPageCode() <= 1) {sb.append("<span style=\"color: #555;\">上一页</span> ");} else {sb.append("<a href=\"" + url + "?page=" + (pageBean.getPageCode() - 1) + "\">上一页</a> ");}//显示页码int begin, end;if (pageBean.getTotalPage() <= 10) {begin = 1;end = pageBean.getTotalPage();} else {begin = pageBean.getPageCode() - 5;end = pageBean.getPageCode() + 4;if (begin < 1) {begin = 1;end = 10;} else if (end > pageBean.getTotalPage()) {begin = pageBean.getTotalPage() - 9;end = pageBean.getTotalPage();}}for (int i = begin; i <= end; i++) {if (i == pageBean.getPageCode()) {sb.append("<span style=\"color:red;\">" + i + "</span> ");} else {sb.append("<a href=\"" + url + "?page=" + i + "\">[" + i + "]</a> ");}}//下一页if (pageBean.getPageCode() >= pageBean.getTotalPage()) {sb.append("<span style=\"color: #555;\">下一页</span>");} else {sb.append("<a href=\"" + url + "?page=" + (pageBean.getPageCode() + 1) + "\">下一页</a> ");}//尾页sb.append("<a href=\"" + url + "?page=" + pageBean.getTotalPage() + "\">尾页</a> \n" +"    页码" + pageBean.getPageCode() + "/" + pageBean.getTotalPage());pageContext.getOut().print(sb.toString());} catch (IOException e) {e.printStackTrace();}return super.doStartTag();}
}RequestPage
package utils;public class RequestPage {public static final int PAGE_SIZE =5;public static Integer getPage(Integer page){if (page==null||page<1){page=1;}return page;}}

datetag.tld

<?xml version="1.0" encoding="utf-8"?><taglib xmlns="http://java.sun.com/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"version="2.1"><tlib-version>1.0</tlib-version><short-name>myshortname</short-name><uri>http://mycompany.com</uri><tag><name>date</name><tag-class>utils.DateTag</tag-class><body-content>empty</body-content><attribute><name>format</name><required>false</required></attribute><attribute><name>color</name><required>false</required></attribute><attribute><name>fontSize</name><required>false</required></attribute></tag><tag><name>page</name><tag-class>utils.PageTag</tag-class><body-content>empty</body-content><attribute><name>pageBean</name><required>false</required><rtexprvalue>true</rtexprvalue></attribute><attribute><name>url</name><required>false</required><rtexprvalue>true</rtexprvalue></attribute></tag></taglib>

book.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="z" uri="http://mycompany.com" %>
<link rel="stylesheet" href="${pageContext.request.contextPath}/css/book.css">
<html>
<head><title>图书</title>
</head>
<body>
<h1 align="center">图书列表</h1>
<hr>
<table><tr><th>ID</th><th>书名</th><th>价格</th></tr><c:forEach var="book" items="${pageBean.pageList}"><tr><td>${book.id}</td><td>${book.bookname}</td><td>${book.price}</td></tr></c:forEach>
</table>
<div id="page"><z:page url="${pageContext.request.contextPath}/book/query" pageBean="${pageBean}"></z:page>
</div>
</body>
</html>

运行显示

分享结束

后面我会持续分享SSM框架知识，欲知后文如何，请看下回分解

*****************************************************************************************************

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