MyBatis——07复习MyBatis过程设计

MyBatis过程设计

1.创建数据库

CREATE TABLE people(
id int(10) PRIMARY KEY auto_increment COMMENT '编号',
name VARCHAR(20) COMMENT '姓名',
age int(3) COMMENT '年龄'
) COMMENT '人员信息表';

INSERT into people VALUES(DEFAULT,'代红2',18);
INSERT into people VALUES(DEFAULT,'代红1',18);

2.写出实体类

package com.youdian.pojo;

public class people {
	private int id;
	private String name;
	private int age;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	
}

3.构建mybatis环境

1. 首先导入jar包，包括mybatis相关的包，数据库的包，JSTL的包
2. 创建全局配置文件，把DTD导入

<!DOCTYPE configuration
  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-config.dtd">

全局配置文件mybatis如下：

<?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>
	<environments default="default">
		<environment id="default">
			<transactionManager type="JDBC"></transactionManager>
			<dataSource type="POOLED">
				<property name="driver" value="com.mysql.jdbc.Driver"/>
				<property name="url" value="jdbc:mysql://localhost:3306/sum"/>
				<property name="username" value="root"/>
				<property name="password" value="root"/>
			</dataSource>
		</environment>
	</environments>
	<mappers>
		<mapper resource="com/youdian/mapper/PeopleMapper.xml"/>
	</mappers>
</configuration>

3. 新建资源文件PeopleMapper.xml，导入mapper的DTD

<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

资源文件内容如下：

<?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.youdian.mapper.PeopleMapper">
	<select id="selAll" resultType="com.youdian.pojo.People">
	select * from people
	</select>
</mapper>

4. 把资源文件的路径复制到全局配置文件mybatis.xml中，完成了数据访问层mapper(相当于以前的dao)

4.写出业务逻辑层(service)

1. 创建接口PeopleService

package com.youdian.service;

import java.util.List;

import com.youdian.pojo.people;

public interface PeopleService {
	/**
	 * 显示全部
	 * @return
	 */
	List<people> show();
}

2. 在PeopleService的实现类PeopleServiceImpl中加载配置文件，因为mybatis默认不加载配置文件
   Resources.getResourceAsStream(“xxx”)
   xxx从classes开始找，在项目中是src文件夹开始
   SqlSession是所有mybatis封装的对象，增删改查都在里面

package com.youdian.service.impl;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

import org.apache.ibatis.builder.xml.XMLConfigBuilder;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import com.youdian.pojo.people;
import com.youdian.service.PeopleService;
/**
 * 在数据访问层处理异常和在控制器中处理异常
 * 在service中只抛出异常
 * 
 *
 */
public class PeopleServiceImpl implements PeopleService{

	public List<people> show() throws IOException {
		InputStream is = Resources.getResourceAsStream("mybatis.xml");
		//前面是工厂       实例化工厂对象时使用的是  构建者设计模式   名称标志:后面有Builder
		//构建者设计模式意义: 简化对象实例化过程
		SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);
/*		等效为上面的一句话
		XMLConfigBuilder parser = new XMLCofigBuilder(is);
		Configuration cfg = parser.parse();
		DefaultSqlSessionFatory factory2= new DefaultSqlSessionFatory(cfg);
**/	
		SqlSession session = factory.openSession();
		List<people> list = session.selectList("com.youdian.mapper.PeopleMapper.selAll");
		session.close();
		return list; 
	}

}

3. 在service接口类中需要抛出PeopleServiceImpl类的异常

package com.youdian.service;

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

import com.youdian.pojo.people;

public interface PeopleService {
	/**
	 * 显示全部
	 * @return
	 */
	List<people> show() throws IOException;
}

5.控制器层

package com.youdian.servlet;

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

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

import com.youdian.pojo.people;
import com.youdian.service.PeopleService;
import com.youdian.service.impl.PeopleServiceImpl;

@WebServlet("/show")
public class ShowServlet extends HttpServlet{
	private PeopleService peopleService = new PeopleServiceImpl();

	protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		List<people> list = peopleService.show();
		req.setAttribute("list", list);
		req.getRequestDispatcher("/index.jsp").forward(req, resp);
	}
}

注1：

1. 大部分注解都有默认属性,如果注解中只给默认属性复制,可以省略属性名
2. 否则在注解的(属性名=属性值)格式
3. 如果一个属性是数组类型格式: 属性名={值,值} ,如果该数组只有一个值,可以省略大括号
4. 如果类型不是基本数据类型或String而是一个类类型,语法: 属性名[email protected]类型
5. 注解中@表示引用注解声明

---

注2：

1. 只要路径中以/开头的都叫做全路径. 从项目根目录(WebContent)出发找到其他资源的过程
2. 只要不以/开头都是相对路径,相对路径是从当前资源出发找到其他资源的过程
3. 如果请求转发 / 表示WebContent目录
4. 如果是重定向,静态资源引用,必须

 <img src=""/> <a href="">  <script src=""/> css引用时 

5. 其中 /都表示的是tomcat的webapps文件夹根目录，即为服务器根目录。
   需要——/虚拟项目名/xxx…
6. jsp运行原理：
   .jsp->.java->.class->编译运行产生流数据，把流返回给浏览器
7. 浏览器解析流后，如果发现有静态资源，再去发送异步请求

6.显示

1. 引入taglib

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<table>
	<tr>
		<th>编号</th>
		<th>姓名</th>
		<th>年龄</th>
	</tr>
	<c:forEach items="${list }" var="peo">
		<tr>
			<td>${peo.id }</td>
			<td>${peo.name }</td>
			<td>${peo.age }</td>
		</tr>
	</c:forEach>
</table>
</body>
</html>