初探MyBatis

〇、什么是MyBatis？

MyBatis是一个持久化层框架，和Spring MVC + Spring Boot + MyBatis一起构成Java Web开发目前最流行的三件套。它支持定制化SQL、存储过程以及高级映射，避免了几乎所有的JDBC代码和手动设置参数以及获取结果集。可以使用简单的XML或注解来配置和映射原生信息，将接口和Java的POJOs（Plain Old Java Objects，普通的Java对象）映射成数据库中的记录。

一、快速使用

1.在Spring Boot maven项目的pom.xml将其依赖引入。

2.在application.properties配置文件中添加如下代码，进行数据源url、username、password和相关文件的配置。

spring.datasource.url=jdbc:mysql://localhost:3306/dbname?useUnicode=true&characterEncoding=utf8&useSSL=false
spring.datasource.username=username
spring.datasource.password=password
mybatis.config-location=classpath:mybatis-config.xml

3.在application.properties同目录下建立mybatis-config.xml文件，其内容如下

<?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>

    <settings>
        <!-- Globally enables or disables any caches configured in any mapper under this configuration -->
        <setting name="cacheEnabled" value="true"/>
        <!-- Sets the number of seconds the driver will wait for a response from the database -->
        <setting name="defaultStatementTimeout" value="3000"/>
        <!-- Enables automatic mapping from classic database column names A_COLUMN to camel case classic Java property names aColumn -->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
        <!-- Allows JDBC support for generated keys. A compatible driver is required.
        This setting forces generated keys to be used if set to true,
         as some drivers deny compatibility but still work -->
        <setting name="useGeneratedKeys" value="true"/>
    </settings>

    <!-- Continue going here -->

</configuration>

4.建立相关模型实体类，比如User.class，里面包含属性的设置和提取等

package com.nowcoder.toutiao.model;


public class User {
    private int id;
    private String name;
    private String password;
    private String salt;
    private String headUrl;

    public User() {

    }
    public User(String name) {
        this.name = name;
        this.password = "";
        this.salt = "";
        this.headUrl = "";
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getSalt() {
        return salt;
    }

    public void setSalt(String salt) {
        this.salt = salt;
    }

    public String getHeadUrl() {
        return headUrl;
    }

    public void setHeadUrl(String headUrl) {
        this.headUrl = headUrl;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }
}

5.编写对该实体类的数据访问DAO，之后便可以通过该DAO实现对数据库的操作

package com.nowcoder.toutiao.dao;

import com.nowcoder.toutiao.model.User;
import org.apache.ibatis.annotations.*;
import org.springframework.stereotype.Repository;


@Mapper
@Repository
public interface UserDAO {
    String TABLE_NAME = "user";
    String INSET_FIELDS = " name, password, salt, head_url ";
    String SELECT_FIELDS = " id, name, password, salt, head_url";

    @Insert({"insert into ", TABLE_NAME, "(", INSET_FIELDS,
            ") values (#{name},#{password},#{salt},#{headUrl})"})
    int addUser(User user);

    @Select({"select ", SELECT_FIELDS, " from ", TABLE_NAME, " where id=#{id}"})
    User selectById(int id);

    @Select({"select ", SELECT_FIELDS, " from ", TABLE_NAME, " where name=#{name}"})
    User selectByName(String name);

    @Update({"update ", TABLE_NAME, " set password=#{password} where id=#{id}"})
    void updatePassword(User user);

    @Delete({"delete from ", TABLE_NAME, " where id=#{id}"})
    void deleteById(int id);
}

参考文献：

http://www.mybatis.org/mybatis-3/zh/index.html