Mybatis的使用（1）

1：新建maven项目，file->project->maven

2：在建好的maven项目中，打开pom.xml文件，加入mybatis所需要的依赖：

<!--    mybatis核心包-->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.2</version>
    </dependency>
<!--    java连接数据库-->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.47</version>
    </dependency>

<!--    单元测试-->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>

3：由于涉及到静态资源的导出问题，故需要在pom.xml中加入如下代码

<!--    静态资源导出问题-->
    <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>

4：由于未涉及到spring，springmvc等，故三层架构先建立一层，也就是dao层（数据层），在dao层建立一个接口（userMapper），然后再新建一个userMapper.xml文件，方便动态代理模式的使用

5：在mysql中建立一张用户表（user），包含id，name，pwd等三个简单字段

6：在建立一个JavaBean，建立一个pojo包，包中建立一个user实体类，与数据库中的user表对应。如下所示：

public class User {
    private Integer Id;
    private String name;
    private String pwd;

    public User() {
    }

    public User(Integer id, String name, String pwd) {
        Id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public User(String name, String pwd) {
        this.name = name;
        this.pwd = pwd;
    }

    public Integer getId() {
        return Id;
    }

    public void setId(Integer id) {
        Id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "Id=" + Id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

7：准备工作完毕，下面需要建立一些xml文件和properties文件：

8：在resource包下建立database.properties文件（作用是为了连接数据库）以及mybatis.xml文件(mybatis核心配置文件)

database.properties文件：

driver=com.mysql.jdbc.Driver
url=jdbc:mysql:///mybatis?useSSL=false&useServerPrepStmts=true&useUnicode=true&characterEncoding=utf-8
username=root
password=ztb

mybatis.xml文件：

<?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>
<!--数据库的资源路径-->
    <properties resource="db.properties"></properties> 
<!--    别名-->
    <typeAliases> 
    <package name="com.ztb.pojo"/></typeAliases>
    
    <environments default="mysql">
        <environment id="mysql">
<!--            事务交给程序员来做-->
            <transactionManager type="JDBC"></transactionManager>
<!--            mybatis中默认的连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>

        </environment>
    </environments>
<!--    注册usermapper-->
 <mappers>
     <mapper class="com.ztb.dao.UserMapper"></mapper>
 </mappers>
</configuration>

9：在userMapper接口处写访问数据库的增删改查方法，方便userMapper.xml调用。（注意：接口和xml文件的名字一定要一样）

public interface UserMapper {
    //查询所有用户
    List<User> seleteAll();

    //根据Id查找用户
    User selectById(int id);
   //增加用户
    int addUser(User user);
//删除用户
    int deleteById(int id);
// 更新用户
    int update(User user);
}

10：在userMapper中写下相应的增删改查语句。

<?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.ztb.dao.UserMapper">

    <select id="seleteAll" resultType="com.ztb.pojo.User">
        select * from mybatis.user
    </select>

    <select id="selectById" resultType="com.ztb.pojo.User" parameterType="int">
        select * from mybatis.user where id= #{id}
    </select>

    <insert id="addUser" parameterType="com.ztb.pojo.User">
        insert into mybatis.user (id,name,pwd) values (#{id},#{name},#{pwd})
    </insert>

    <delete id="deleteById" parameterType="int">
        delete from mybatis.user where id=#{id}
    </delete>

    <update id="update" parameterType="com.ztb.pojo.User">
        update mybatis.user set name=#{name},pwd=#{pwd} where id=#{id};
    </update>
</mapper>

11：至此，一切准备工作完毕，下面开始测试增删改查

12：在test文件下新建测试类：

public class Test1 {
    SqlSession sqlSession=null;

    @Before
    public void Before1() throws IOException {
        InputStream inputStream = Resources.getResourceAsStream("mybaits.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        sqlSession = sqlSessionFactory.openSession();

    }
    @After
    public void after(){
        sqlSession.close();
    }

    @Test
    public void test11() throws IOException {

        UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
        List<User> users = userMapper.seleteAll();
        for (User user : users) {
            System.out.println(user);
        }
    }
    @Test
    public void test12(){
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.selectById(2);
        System.out.println(user);

    }
    @Test
    public void test13(){
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int i = mapper.addUser(new User(8,"张三", "123456"));
        sqlSession.commit();
        System.out.println(i);

    }
    @Test
    public void test14(){
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int i = mapper.deleteById(8);
        sqlSession.commit();
        System.out.println(i);

    }
    @Test
    public void test15(){
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int i = mapper.update(new User(0,"张三","111111"));
        sqlSession.commit();
        System.out.println(i);

    }
}