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javaweb_forQuery

学习内容链接

http://how2j.cn/k/tmall_ssm/tmall_ssm-1516/1516.html

总体思路

使用springMVC+spring+mybatis的方式打通表现层/业务层/持久层。从浏览器接收访问路径开始,经过数据库调取数据(只做查询),最后从浏览器显示视图的全部简易流程。

开发环境

  • Eclipse oxygen
  • tomcat 8.5
  • Apache maven 3.5.3
  • mysql

实现步骤

  1. 环境配置完成后,启动Maven新建webapp项目
  2. 在pom.xml中添加依赖(依赖来源:Maven Repository

依赖清单:

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<properties>
<spring.version>4.1.3.RELEASE</spring.version>
<pagehelper.version>5.1.2-beta</pagehelper.version>
<mysql.version>5.1.6</mysql.version>
<mybatis.spring.version>1.2.3</mybatis.spring.version>
<mybatis.version>3.1.1</mybatis.version>
<junit.version>4.12</junit.version>
<jstl.version>1.2</jstl.version>
<jsqlparser.version>1.0</jsqlparser.version>
<jackson.version>1.2.7</jackson.version>
<servlet-api.version>3.1.0</servlet-api.version>
<druid.version>1.0.18</druid.version>
<log4j.version>1.2.16</log4j.version>
<commons-logging.version>1.2</commons-logging.version>
<commons-fileupload.version>1.2.1</commons-fileupload.version>
<commons-io.version>1.3.2</commons-io.version>
<commons-lang.version>2.6</commons-lang.version>
<aopalliance.version>1.0</aopalliance.version>
<mybatis-generator.version>1.3.5</mybatis-generator.version>
</properties>
  1. 创建实体类Category,定义了private的id和name,以及getter/setter方法

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    public class Category {
    private Integer id;
    private String name;
    public Integer getId() { return id; }
    public void setId(Integer id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    }
  1. 创建接口CategoryMapper,申明list方法,未来可以添加增删改查等操作

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    public interface CategoryMapper {
    List<Category> list();
    }
  2. 创建接口CategoryService,申明list方法

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    public interface CategoryService {
    List<Category> list();
    }
  3. 创建类CategoryServiceImpl实现CategoryService接

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    @Service
    public class CategoryServiceImpl implements CategoryService {
    @Autowired
    CategoryMapper categoryMapper;
    @Override
    public List<Category> list() { return categoryMapper.list(); }
    }

@Service 表示将CategoryServiceImpl类交给spring来管理,并申明为Service类
@Autowired 表示由spring自动装配注入categoryMapper

  1. 创建类CategoryController,处理请求,跳转视图

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    @Controller
    @RequestMapping("")
    public class CategoryController {
    @Autowired
    CategoryService categoryService;

    //处理admin_category_list路径的url
    @RequestMapping("admin_category_list")
    public String list(Model model) {
    List<Category> cs=categoryService.list();
    //向
    model.addAttribute("cs",cs);

    //视图跳转到listCategory.jsp文件
    return "admin/listCategory";
    }
    }
  2. 创建CategoryMapper.xml配置文件,实现id倒排序查询所有分类

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    <mapper namespace="com.ihappy.lee.mapper.CategoryMapper">
    //id="list"唯一标识此sql语句,并与接口方法名保持一致
    <select id="list" resultType="Category">
    select * from category order by id desc
    </select>
    </mapper>
  3. 创建核心文件applicationContext.xml–对注解的识别;对jdbc.properties的引用;指定数据库连接池;配置Mybatis的SessionFactory;

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    <context:component-scan base-package="com.ihappy.lee.service" />


    <context:property-placeholder location="classpath:jdbc.properties"/>

    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
    <property name="url" value="${jdbc.url}" />
    <property name="username" value="${jdbc.username}" />
    <property name="password" value="${jdbc.password}" />
    </bean>

    <bean id="sqlSession" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="typeAliasesPackage" value="com.ihappy.lee.pojo" />
    <property name="dataSource" ref="dataSource"/>
    <property name="mapperLocations" value="classpath:mapper/*.xml"/>
    </bean>
  4. 创建springMVC.xml

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    <!--springMVC的注解配置-->
    <context:annotation-config/>
    <!-- base-package后跟要扫描的包 expression是注解类的全名 -->
    <context:component-scan base-package="com.ihappy.lee.controller">
    <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
    </context:component-scan>
    <mvc:annotation-driven />

    <!--开通静态资源的访问-->
    <mvc:default-servlet-handler />

    <!-- 视图定位到/WEB-INF/jsp目录下 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" />
    <property name="prefix" value="/WEB-INF/jsp/" />
    <property name="suffix" value=".jsp" />
    </bean>

    <!-- 对上传文件的解析-->
    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"/>
  5. 配置web.xml–指定spring核心配置文件applicationContext.xml;设置中文过滤器;分发servlet,指定springMVC配置文件springMVC.xml

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    <!-- spring的配置文件-->
    <context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>classpath:applicationContext.xml</param-value>
    </context-param>
    <listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <!--中文过滤器-->
    <filter>
    <filter-name>CharacterEncodingFilter</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>CharacterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
    </filter-mapping>

    <!-- spring mvc核心:分发servlet -->
    <servlet>
    <servlet-name>mvc-dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <!-- spring mvc的配置文件 -->
    <init-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>classpath:springMVC.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
    <servlet-name>mvc-dispatcher</servlet-name>
    <url-pattern>/</url-pattern>
    </servlet-mapping>
  6. 其他配置(日志文件log4j.properties;数据库配置文件jdbc.properties),略

  7. 使用的静态资源,略
  8. 创建listCategory.jsp文件

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    <!--  关键代码:
    遍历cs里的内容,然后挨个显示出来 -->
    <c:forEach items="${cs}" var="c">
  9. 简易测试类

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    public static void main(String args[]) {
    try {
    Class.forName("com.mysql.jdbc.Driver");
    } catch (ClassNotFoundException e) {
    e.printStackTrace();
    }
    try (Connection c = DriverManager.getConnection(
    "jdbc:mysql://localhost:3306/tmall_ssm?useUnicode=true&characterEncoding=utf8", "root", "admin");
    Statement s = c.createStatement();) {
    for(int i=0;i<=10;i++) {
    String sqlFormat="insert into category values (null,'测试分类%d')";
    String sql=String.format(sqlFormat, i);
    s.execute(sql);
    }
    }catch(SQLException e) {
    e.printStackTrace();
    }
    }

运行思路

  1. 从浏览器上访问路径/admin_category_list
  2. 根据web.xml中的配置(分发servlet),将拦截到的/admin_category_list,交给DispatcherServlet来处理

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    <servlet-mapping>
    <servlet-name>mvc-dispatcher</servlet-name>
    <url-pattern>/</url-pattern>
    </servlet-mapping>

【注】“url-pattern”使用的’/‘将会覆盖到容器的default servlet,凡是web.xml中找不到匹配的URL,访问请求都将交给该servlet,即DispatcherServlet来处理

  1. DispatcherServlet根据springMVC的配置(扫描注解),将这次请求交由CategoryController类来处理,映射到该类的list方法上(list方法带有@RequestMapping(“admin_category_list”)注解)
  2. CategoryController自动注入CategoryService,在访问了categoryService.list()方法时,再自动注入CategoryMapper
  3. 根据applicationContext.xml配置的会话工厂SessionFactory,使用mapperLocations属性来指定resources/mapper下的xml文件,将读取的CategoryMapper.xml与CategoryMapper关联起来
  4. 通过步骤4、5完成CategoryController的实例化,使用CategoryController.list()处理查询请求,id为‘list’的sql语句被执行,将查询结果封装到Category对象,并存入List类型的cs中
  5. 把集合cs放入model中传递给jsp,之后跳转到admin/listCategory.jsp页面,经过foreach把List项逐个显示出来

forquery.png

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