SSM整合
SSM框架整合
环境
- IDEA
- MySQL 5.5
- Tomcat 8.5.34
- Maven 3.6.0
搭建数据库(MySQL)
CREATE DATABASE `ssmbuild`;
USE `ssmbuild`;
DROP TABLE IF EXISTS `books`;
CREATE TABLE `books` (
`bookID` INT(10) NOT NULL AUTO_INCREMENT COMMENT '书id',
`bookName` VARCHAR(100) NOT NULL COMMENT '书名',
`bookCounts` INT(11) NOT NULL COMMENT '数量',
`detail` VARCHAR(200) NOT NULL COMMENT '描述',
KEY `bookID` (`bookID`)
) ENGINE=INNODB DEFAULT CHARSET=utf8
INSERT INTO `books`(`bookID`,`bookName`,`bookCounts`,`detail`)VALUES
(1,'Java',1,'从入门到放弃'),
(2,'MySQL',10,'从删库到跑路'),
(3,'Linux',5,'从入门到进牢');
基本项目的搭建
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新建maven项目,添加web支持
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导入相关的maven依赖
<dependencies> <!--Junit--> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> </dependency> <!--数据库驱动--> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.47</version> </dependency> <!-- 数据库连接池 --> <dependency> <groupId>com.mchange</groupId> <artifactId>c3p0</artifactId> <version>0.9.5.2</version> </dependency> <!--Servlet - JSP --> <dependency> <groupId>javax.servlet</groupId> <artifactId>servlet-api</artifactId> <version>2.5</version> </dependency> <dependency> <groupId>javax.servlet.jsp</groupId> <artifactId>jsp-api</artifactId> <version>2.2</version> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>jstl</artifactId> <version>1.2</version> </dependency> <!--Mybatis--> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.2</version> </dependency> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis-spring</artifactId> <version>2.0.2</version> </dependency> <!--Spring--> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>5.1.9.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-jdbc</artifactId> <version>5.1.9.RELEASE</version> </dependency> </dependencies>
3.Maven资源过滤问题
<build> <resources> <resource> <directory>src/main/java</directory> <includes> <include>**/*.properties</include> <include>**/*.xml</include> </includes> <filtering>false</filtering> </resource> <resource> <directory>src/main/resources</directory> <includes> <include>**/*.properties</include> <include>**/*.xml</include> </includes> <filtering>false</filtering> </resource> </resources> </build>
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建立基本结构和配置框架
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com.inspur.pojo (持久层)
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com.inspur.dao (Dao层)
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com.inspur.service (业务处理层)
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com.inspur.controller (业务控制层)
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mybatis-config.xml (可在IDEA中设置xml模版) --> File | Settings | 编辑器 | 文件和代码模板
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <!-- 别名设置 pojo:实体类上可加注解 @Alias("books")--> <!--可在Mapper.xml文件中使用时无需类的全限定名,默认为类名 --> <typeAliases> <package name=""/> </typeAliases> <!-- mapper文件路径 --> <mappers> <mapper resource=""></mapper> </mappers> </configuration>
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applicationContext.xml (IDEA含有spring的初始化的配置文件)
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> </beans>
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Mybatis层
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数据库配置文件db.properties (设为模版,同上), --> 在Spring配置文件中读取
jdbc.driver=com.mysql.jdbc.Driver #如果使用MySQL8.0+,需要增加一个时区的配置; &serverTimezone=Asia/Shanghai jdbc.url=jdbc:mysql://localhost:3306/ssmbuild?useSSL=true&useUnicode=true&characterEncoding=utf8 jdbc.username=root jdbc.password=123456
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IDEA关联数据库(idea自带的数据库链接)
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编写(完善配置信息 注意标签的顺序)MyBatis的核心配置文件(mybatis-config.xml)
<!-- 标准的 日志工厂实现 --> <settings> <setting name="logImpl" value="STDOUT_LOGGING"/> <!-- 是否开启自动驼峰命名规则 (camel case)映射 --> <!-- <setting name="mapUnderscoreToCamelCase" value="true"/>--> <!-- 开启全局缓存 --> <setting name="cacheEnabled" value="true"/> </settings> <typeAliases> <package name="com.inspur.pojo"/> </typeAliases> <mappers> <mapper resource="com.inspur.dao.BookNapper.xml"/> </mappers>
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编写数据库对应的实体类com.inspur.pojo.Books
使用Lombok插件
import lombok.AllArgsConstructor; import lombok.Data; import lombok.NoArgsConstructor; import org.apache.ibatis.type.Alias; import java.io.Serializable; /** * @author 12093 * @Created by 12093 */ @Data @AllArgsConstructor @NoArgsConstructor @Alias("books") //可在Mapper.xml文件中使用,无需类的全限定名 public class Books implements Serializable { //我们需要将实体类序列化(implements Serializable)!否则就会报错! private int bookID; private String bookName; private int bookCounts; private String detail; }
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编写Dao层的Mapper接口
import com.inspur.pojo.Books; import org.apache.ibatis.annotations.Param; import java.util.List; /** * @author 12093 */ public interface BookMapper { //实现 增/删/改/查 // 增加一本书 int addBook(Books books); // 删除一本书 int deleteBookById(@Param("bookID") int id); // 更新一本书 int updateBookById(Books books); // 查询一本书 Books queryBookById(@Param("bookID") int id); // 查询全部的书 List<Books> queryAllBook(); //根据ID查询一本书 List queryBookByName(@Param("bookName") String bookName); }
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编写接口对应的Mapper.xml文件(最好与其接口 同名/同路径)
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <!-- MyBatis映射文件 --> <!--namespace=绑定一个对应的Dao/Mapper接口--> <mapper namespace="com.inspur.dao.BookMapper"> <cache/> <!-- 设置此xml文件,使用二级缓存 --> <!--增加一个Book--> <insert id="addBook" parameterType="Books"> insert into books (bookName,bookCounts,detail) values (#{bookName},#{bookCounts},#{detail}); </insert> <!--根据id删除一个Book--> <delete id="deleteBookById" parameterType="int"> delete from books where bookID = #{bookID} </delete> <!--更新Book--> <update id="updateBookById" parameterType="Books"> update books set bookName=#{bookName},bookCounts=#{bookCounts},detail=#{detail} where bookID=#{bookID}; </update> <!--根据id查询,返回一个Book--> <select id="queryBookById" resultType="Books"> select * from books where bookID = #{bookID} </select> <!--查询全部Book--> <select id="queryAllBook" resultType="Books"> select * from books; </select> <!--根据bookName查询,返回一个Book--> <select id="queryBookByName" resultType="Books"> select * from books where bookName like "%"#{bookName}"%" </select> </mapper>
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编写Service层的接口和实现类
接口:
package com.inspur.service; import com.inspur.pojo.Books; import java.util.List; /** * @author 12093 * @Classname BookService * @Date 2020/11/8 22:58 * BookService:底下需要去实现,调用dao层 */ public interface BookService { // 增加一本Book int addBook(Books books); //根据id删除一本书Book int deleteBookById(int id); // 更新Book int updateBookById(Books books); //根据ID查询,返回一个Book Books queryBookById(int id); //查询全部Book,返回list集合 List<Books> queryAllBook(); //根据书名模糊查询一本书 List<Books> queryBookByName(@Param("bookName") String bookName); }
实现类:
```java
mport com.inspur.dao.BookMapper;
import com.inspur.pojo.Books;
import java.util.List;
public class BookServiceImpl implements BookService{
//service调dao层: 组合Dao 可添加业务
private BookMapper bookMapper;
public void setBookMapper(BookMapper bookMapper) {
this.bookMapper = bookMapper;
}
@Override
public int addBook(Books books) {
return bookMapper.addBook(books);
}
@Override
public int deleteBookById(int id) {
return bookMapper.deleteBookById(id);
}
@Override
public int updateBookById(Books books) {
return bookMapper.updateBookById(books);
}
@Override
public Books queryBookById(int id) {
return bookMapper.queryBookById(id);
}
@Override
public List<Books> queryAllBook() {
return bookMapper.queryAllBook();
}
@Override
public List<Books> queryBookByName(String bookName) {
return bookMapper.queryBookByName(bookName);
}
}
底层需求操作完毕
Spring层
🕶️注意事项: 所有的Spring的配置文件,配置的应用程序上下文在一个文件中
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配置
Spring整合MyBatis
,这里使用c3p0连接池; -
我们去编写Spring整合MyBatis的相关配置文件; Spring-dao.xml (多个Spring配置文件,整合,分层管理)
<?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" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd"> <!-- DataSource:使用Spring的数据源替换MyBatis的配置 c3p0/dbcp/druid--> <!-- 1.关联数据库配置文件--> <context:property-placeholder location="classpath:db.properties"/> <!-- 2.连接池 dbcp:半自动化操作,不能自动连接 c3p0: 自动化操作(自动化的加载配置文件,并且可以自动设置到对象中!) druid: hikari: --> <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"> <property name="driverClass" value="${jdbc.driver}"/> <property name="jdbcUrl" value="${jdbc.url}"/> <property name="user" value="${jdbc.username}"/> <property name="password" value="${jdbc.password}"/> <!-- c3p0连接池的私有属性 可默认不使用--> <property name="maxPoolSize" value="30"/> <property name="minPoolSize" value="10"/> <!-- 关闭连接后不自动commit --> <property name="autoCommitOnClose" value="false"/> <!-- 获取连接超时时间 --> <property name="checkoutTimeout" value="10000"/> <!-- 当获取连接失败重试次数 --> <property name="acquireRetryAttempts" value="2"/> </bean> <!-- 3.配置sqlSessionFactory对象--> <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"> <!-- 注入数据库连接池 --> <property name="dataSource" ref="dataSource"/> <!-- 配置MyBatis的全局配置文件:mybatis-config.xml --> <property name="configLocation" value="classpath:mybatis-config.xml"/> </bean> <!-- 4. 配置dao接口扫描包,动态的实现了Dao接口可以注入到Spring容器中! --> <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"> <!-- 注入sqlSessionFactory--> <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"/> <!-- 给出需要扫描的Dao接口包 --> <property name="basePackage" value="com.inspur.dao"/> </bean> </beans>
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Spring整合Service层
<?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" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd"> <!-- 1. 扫描service下的包 --> <context:component-scan base-package="com.inspur.service"/> <!-- 2. 将我们的所有业务类,注入到springIOC容器中,可以通过配置,或者注解实现--> <!-- BookServiceImpl 注入到 IOC容器中 --> <bean id="BookServiceImpl" class="com.inspur.service.BookServiceImpl"> <property name="bookMapper" ref="bookMapper"/> </bean> <!-- 3. 配置事务管理器 --> <bean id="TransactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"> <!-- 注入数据源 --> <property name="dataSource" ref="dataSource"/> </bean> </beans>
Spring层搞定! Spring就是一个大杂烩,一个容器!
SpringMVC层
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web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" version="4.0"> <!-- DispatchServlet --> <servlet> <servlet-name>DispatcherServlet</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <!-- 一定要注意: 这里加载的是总的配置文件!!! 不是Spring-mvc.xml --> <param-value>classpath:applicationContext.xml</param-value> </init-param> <!-- 启动优先级 --> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>DispatcherServlet</servlet-name> <url-pattern>/</url-pattern> <!-- "/",处理所有文件; "/*"不处理.jsp文件 --> </servlet-mapping> <!-- 乱码过滤 encodingFilter --> <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> </filter> <filter-mapping> <filter-name>encodingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <!-- Session过期时间 --> <session-config> <session-timeout>15</session-timeout> </session-config> </web-app>
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spring-mvc.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:nvc="http://www.springframework.org/schema/mvc" xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd"> <!-- 配置SpringMVC --> <!-- 1.开启SpringMVC注解驱动 --> <nvc:annotation-driven/> <!-- 2.静态资源过滤默认servlet配置 --> <mvc:default-servlet-handler/> <!-- 3.扫描web相关的bean:controller --> <context:component-scan base-package="com.inspur.controller"/> <!-- 4.配置jsp显示ViewResolver试图解析器 --> <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="prefix" value="/WEB-INF/jsp"/> <property name="suffix" value=".jsp"/> </bean> </beans>
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Spring配置整合文件,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" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <!-- 整合配置文件 --> <import resource="classpath:spring-dao.xml"/> <import resource="classpath:spring-service.xml"/> <import resource="classpath:spring-mvc.xml"/> </beans>
配置文件,暂时结束! Controller 和 视图层编写
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BookController类编写, 一、查询所有书籍
@Controller @RequestMapping("/book") public class BookController { @Autowired @Qualifier("BookServiceImpl") private BookService bookService; /// 查询全部书籍,并发挥到一个书籍的展示页面 @RequestMapping("/allBook") //查询所有Book public String list(Model model){ List<Books> list = bookService.queryAllBook(); model.addAttribute("list",list); return "allBook"; }
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编写首页index.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %> <!DOCTYPE HTML> <html> <head> <title>首页</title> <style type="text/css"> a { text-decoration: none; color: black; font-size: 18px; } h3 { width: 180px; height: 38px; margin: 100px auto; text-align: center; line-height: 38px; background: deepskyblue; border-radius: 4px; } </style> </head> <body> <h3> <a href="${pageContext.request.contextPath}/book/allBook">点击进入列表页</a> </h3> </body> </html>
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书籍列表展示页面 allbook.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>书籍列表</title> <%-- 引入Bootstrap 美化界面 --%> <link href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"> <%-- Bootstrap框架提供了更好的跨浏览器一致性 --%> <link href="../../css/normalize.css" rel="stylesheet"> </head> <body> <%--边框线--%> <div class="container"> <%-- 清除浮动--%> <div class="row clearfix"> <%-- 把一个列中等(md)屏幕(12份)分成12份 --%> <div class="col-md-12 column"> <%-- 头部 标签--%> <div class="page-header"> <h1> <small>书籍列表----显示所有书籍</small> </h1> </div> </div> <div class="row"> <div class="col-md-4 column"> <a class="btn btn-primary" href="${pageContext.request.contextPath}/book/toAddBook">新增书籍</a> <a class="btn btn-primary" href="${pageContext.request.contextPath}/book/allBook">显示全部书籍</a> </div> <div class="col-md-4 column"></div> <div class="col-md-4 column"> <%-- 查询书籍 --%> <form class="form-inline" action="${pageContext.request.contextPath}/book/queryBook" method="post" style="float: right"> <span style="color: red; font-weight: bold">${error}</span> <input type="text" name="queryBookName" placeholder="请输入要查询的书籍名称" required> <input type="submit" value="查询" class="btn btn-primary"> </form> </div> </div> <div class="row clearfix"> <div class="col-md-12 column"> <%-- table-hover:隔行变色 --%> <table class="table table-hover table-striped"> <thead> <tr> <th>书籍编号</th> <th>书籍名字</th> <th>书籍数量</th> <th>书籍详情</th> <th>操作</th> </tr> </thead> <tbody> <c:forEach var="book" items="${list}"> <tr> <td>${book.getBookID()}</td> <td>${book.getBookName()}</td> <td>${book.getBookCounts()}</td> <td>${book.getDetail()}</td> <td> <a href="${pageContext.request.contextPath}/book/toUpdateBook?id=${book.getBookID()}">修改</a> | <a href="${pageContext.request.contextPath}/book/del/${book.getBookID()}">删除</a> </td> </tr> </c:forEach> </tbody> </table> </div> </div> </div> </body> </html>
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添加书籍
//跳转到添加书籍页面(addBook.jsp) @RequestMapping("/toAddBook") public String toAddPaper(){ return "addBook"; } // 从addBook.jsp页面,返回的书籍数据,添加到数据库 //添加书籍的请求 @RequestMapping("/addBook") public String addPaper(Books books) { System.out.println("books==>"+books); bookService.addBook(books); return "redirect:/book/allBook"; }
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addBook.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>新增书籍</title> <!-- 引入 Bootstrap --> <link href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"> <link href="../../css/normalize.css" rel="stylesheet"> </head> <body> <div class="container"> <div class="row clearfix"> <div class="col-md-12 column"> <div class="page-header"> <h1> <small>新增书籍</small> </h1> </div> </div> </div> <form action="${pageContext.request.contextPath}/book/addBook" method="post"> <div class="form-group"> <label for="bkname">书籍名称:</label> <input type="text" class="form-control" id="bkname" name="bookName" required> </div> <div class="form-group"> <label for="bknum">书籍数量:</label> <input type="text" class="form-control" id="bknum" name="bookCounts" required> </div> <div class="form-group"> <label for="bkdetail">书籍描述:</label> <input type="text" class="form-control" id="bkdetail" name="detail" required> </div> <button type="submit" class="btn btn-primary">添加</button> <a href="${pageContext.request.contextPath}/book/allBook" class="btn btn-default">取消</a> </form> </div> </body> </html>
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修改书籍
///// 方法三:修改书籍 // 先根据ID查询到书籍信息返回至修改页面, // 在updateBook页面 将id设为隐藏域,再将书籍信息更改后重定向到allBook @RequestMapping("/toUpdateBook") public String toUpdateBook(Model model,int id){ Books books = bookService.queryBookById(id); System.out.println(books); model.addAttribute("book",books); return "updateBook"; } @RequestMapping("/updateBook") public String updateBook(Model model,Books book){ System.out.println("updateBook==>"+book); bookService.updateBook(book); Books books = bookService.queryBookById(book.getBookID()); model.addAttribute("books",books); return "redirect:/book/allBook"; }
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updateBook.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>修改信息</title> <!-- 引入 Bootstrap --> <link href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"> <link href="../../css/normalize.css" rel="stylesheet"> </head> <body> <div class="container"> <div class="row clearfix"> <div class="col-md-12 column"> <div class="page-header"> <h1> <small>修改信息</small> </h1> </div> </div> </div> <form action="${pageContext.request.contextPath}/book/updateBook" method="post"> <%-- 修改书籍需要用到BookID 设置隐藏域 --%> <input type="hidden" name="bookID" value="${book.getBookID()}"/> <div class="from-group"> <label>书籍名称:</label> <input class="form-control" type="text" name="bookName" value="${book.getBookName()}" required/> </div> <div class="form-group"> <label>书籍数量:</label> <input class="form-control" type="text" name="bookCounts" value="${book.getBookCounts()}" required/> </div> <div class="form-group"> <label>书籍详情:</label> <input class="form-control" type="text" name="detail" value="${book.getDetail() }" required/> </div> <div class="form-group"> <input class="form-control" type="submit" value="修改"/> </div> <div class="form-group"> <a href="${pageContext.request.contextPath}/book/allBook" class="align-middle form-control">取消</a> </div> </form> </div>
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删除书籍
//// 方法四: 删除书籍 @RequestMapping("/del/{bookId}") public String deleteBook(@PathVariable("bookId") int id){ System.out.println("删除书籍的ID==>"+id); bookService.deleteBookById(id); return "redirect:/book/allBook"; }
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按书名查询书籍(找不到则显示全部书籍,并报错)
///查询书籍 @RequestMapping("/queryBook") public String queryBook(String queryBookName,Model model){ // boolean q = false; List<Books> list = bookService.queryBookByName(queryBookName); for (Books books : list) { //红色输出 System.err.println("queryBookName==>"+books); } if (list.size() == 0){ list = bookService.queryAllBook(); model.addAttribute("error","未查到"); System.out.println("===未查到==="); } model.addAttribute("list",list); return "allBook"; }
小结(MySQL数据库主键无法连续自增问题
)
MySQL数据库:
解决单条数据id自增不连续问题
创建的表的类型为InnoDB类型,为了提升性能设置AUTO_INCREMNT不会回退,因此innoDB使用了不连续的自增值
解决:
使用Mybatis中的标签
<!-- 当用户表为空时,id设置为1
当用户表不为空时,id设置为当前最大id加1 -->
<insert id="addBook" parameterType="Books">
<selectKey keyProperty="bookID" resultType="int" order="BEFORE">
select if(max(bookID) is null,1,max(bookID)+1) as bookID from books
</selectKey>
insert into books (bookID,bookName,bookCounts,detail)
values (#{bookID},#{bookName},#{bookCounts},#{detail});
</insert>