第一种:返回数据给jsp页面
1. 添加依赖
<!--版本号-->
<properties>
<spring-version>5.2.1.RELEASE</spring-version>
<mysql-version>5.1.41</mysql-version>
<jackson-version>2.9.9</jackson-version>
</properties>
<dependencies>
<!--spring-->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>${spring-version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring-version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>${spring-version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring-version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>${spring-version}</version>
</dependency>
<!--mybatis-->
<dependency>
<groupId>tk.mybatis</groupId>
<artifactId>mapper</artifactId>
<version>4.1.5</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.2</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis-spring</artifactId>
<version>2.0.3</version>
</dependency>
<!--mysql-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>${mysql-version}</version>
</dependency>
<!--jstl-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<!--servlet-api-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
</dependency>
2. 完成各项配置
- web.xml配置前端控制器
<?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">
<!--配置前端控制器-->
<servlet>
<servlet-name>dispatcherServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<!--引入配置文件-->
<param-value>classpath:spring.xml</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>dispatcherServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
db.properties
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/jdbctest?serverTimezone
jdbc.username=root
jdbc.password=msj
spring.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:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">
<!--扫包-->
<context:component-scan base-package="com.msj"/>
<!--视图解析器-->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/pages"/>
<property name="suffix" value=".jsp"/>
</bean>
<!--引入db.properties-->
<context:property-placeholder location="classpath:db.properties"/>
<!--配置数据源-->
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</bean>
<!--SqlSessionFactoryBean-->
<bean class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<!--扫描xml配置文件-->
<property name="mapperLocations" value="classpath:mapper/*"/>
</bean>
<!--扫描mapper包-->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.msj.mapper"/>
</bean>
<!--开启注解-->
<mvc:annotation-driven/>
</beans>
UserMapper.xml
<?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" >
<mapper namespace="com.msj.mapper.UserMapper" >
<resultMap id="BaseResultMap" type="com.msj.pojo.User" >
<!--
WARNING - @mbg.generated
-->
<id column="id" property="id" jdbcType="INTEGER" />
<result column="name" property="name" jdbcType="VARCHAR" />
<result column="age" property="age" jdbcType="INTEGER" />
<result column="cid" property="cid" jdbcType="INTEGER" />
</resultMap>
<sql id="Base_Column_List" >
<!--
WARNING - @mbg.generated
-->
id, name, age, cid
</sql>
<select id="findAll" resultMap="BaseResultMap">
select * from user;
</select>
</mapper>
3. 分层编写代码
- 控制层
UserController.java
@Controller
public class UserController {
@Autowired
private UserService userService;
@RequestMapping("/test")
public String test(HttpServletRequest request){
List<User> userList = userService.selectAll();
request.setAttribute("user",userList);
return "/hello";
}
}
- service层
UserService.java
public interface UserService {
List<User> selectAll();
}
UserServiceImpl.java
@Service
public class UserServiceImpl implements UserService {
@Autowired
private UserMapper userMapper;
public List<User> selectAll() {
return userMapper.findAll();
}
}
- mapper层
这里之所以不用写注解,也能扫描得到,是因为在spring.xml中添加配置,如下:
<!--扫mapper包-->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.msj.mapper"/>
</bean>
UserMapper.java
public interface UserMapper{
List<User> findAll();
}
- jsp页面
注意:要添加jstl依赖
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<title>test</title>
</head>
<body>
<h2>hello</h2>
<table>
<tr>
<th>id</th>
<th>name</th>
</tr>
<c:forEach items="${user}" var="i">
<tr>
<th>${i.id}</th>
<th>${i.name}</th>
</tr>
</c:forEach>
</table>
</body>
</html>
结果:
第二种:使用返回json数据
- 在上面例子的基础上进行修改,首先要添加依赖
<!--jackson-->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>${jackson-version}</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>${jackson-version}</version>
</dependency>
不添加对象转json的依赖就会报错:“No converter found for return value of type: class java.util.ArrayList”。
2.在spring.xml添加配置
<!--开启springmvc注解-->
<mvc:annotation-driven/>
如果不开启MVC注解,然后去使用@ResponseBody,也会报错“No converter found for return value of type: class java.util.ArrayList”。
- 在controller层进行修改,添加@ResponseBody注解,将java对象转json
@Controller
public class UserController {
@Autowired
private UserService userService;
@RequestMapping("/test")
@ResponseBody
public List<User> test(){
return userService.selectAll();
}
运行结果:
注意
逆向工程将数据库表生成java类,如果我们使用一个Java类去继承Mapper和MySqlMapper的话,我们在扫描mapper包的时候,就需要进行修改,否则扫描不到会报错。
spring.xml
<!--扫mapper包-->
<!--<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">-->
<!--<property name="basePackage" value="com.msj.mapper"/>-->
<!--</bean>-->
<bean class="tk.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.msj.mapper"/>
</bean>
原因:是因为Mapper类和MySqlMapper是在tk包下的
MyMapper.java
import tk.mybatis.mapper.common.Mapper;
import tk.mybatis.mapper.common.MySqlMapper;
public interface MyMapper<T> extends Mapper<T>, MySqlMapper<T> {
}
mapper包下的UserMapper.java
public interface UserMapper extends MyMapper<User>{
}