創(chuàng)建maven項(xiàng)目叹阔，并分別添加依賴师妙，junit诗祸，mysql血久，mybatis(3.4.6)

在resouces下創(chuàng)建mybatis的配置文件

<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3307/mysqls?serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="LKT981016"/>
            </dataSource>
        </environment>
   </environments>
    <mappers>
        <mapper resource="com/pojo/UsersMapper.xml"/>
    </mappers>
</configuration>

數(shù)據(jù)庫文件 db.sql

CREATE TABLE `user` (
  `uid` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(20) NOT NULL,
  `password` varchar(20) NOT NULL,
  `age` int(11) DEFAULT NULL,
  `addr` varchar(50) DEFAULT NULL,
  PRIMARY KEY (`uid`),
  UNIQUE KEY `username` (`username`)
) ENGINE=InnoDB AUTO_INCREMENT=17 DEFAULT CHARSET=latin1

JavaBean文件 User.java

public class User {
    private int uid;
    private String username;
    private String password;
    private int age;
    private String addr;

    public int getUid() { return uid; }
    public void setUid(int uid) { this.uid = uid; }
    public String getUsername() { return username; }
    public void setUsername(String username) { this.username = username; }
    public String getPassword() { return password; }
    public void setPassword(String password) { this.password = password; }
    public int getAge() { return age; }
    public void setAge(int age) { this.age = age; }
    public String getAddr() { return addr; }
    public void setAddr(String addr) { this.addr = addr; }

    @Override
    public String toString() {
        final StringBuffer sb = new StringBuffer("User{");
        sb.append("uid=").append(uid);
        sb.append(", username='").append(username).append('\'');
        sb.append(", password='").append(password).append('\'');
        sb.append(", age=").append(age);
        sb.append(", addr='").append(addr).append('\'');
        sb.append('}');
        return sb.toString();
    }
}

在com.pojo的包下創(chuàng)建UserMapper.xml文件

<?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.qfedu.pojo.UserMapper">
    <select id="selectUser" resultType="com.qfedu.pojo.User">
      select * from user
    </select>
    <select id="selectUserCount" resultType="int">
      select count(1) from user;
    </select>
    <select id="selectUsersByPage1" resultType="com.qfedu.pojo.User">
        select * from user limit 3
    </select>
    <select id="selectUsersByPage2" resultType="com.qfedu.pojo.User">
        select * from user limit #{pageSize}
    </select>
    <select id="selectUsersByPage3" resultType="com.qfedu.pojo.User">
        select * from user limit #{startIndex}, #{pageSize}
    </select>
    <delete id="saveUser">
        insert into user values(null, #{username}, #{password}, #{age}, #{addr});
    </delete>
    <delete id="deleteUserByUid">
        delete from user where uid = #{uid}
    </delete>
    <update id="updateUser">
        update user set username= #{username}, password=#{password}, age = #{age}, addr = #{addr} where uid = #{uid};
    </update>
</mapper>

測試類 TestUser.java

public class TestUser {
    private SqlSessionFactory sf = null;
    private SqlSession session = null;
    @Before
    public void setUp(){
        try {
            sf = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis.xml"));
            session = sf.openSession(true);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    @After
    public void tearDown(){
        if(session != null){
            session.close();
            session = null;
        }
    }
    @Test
    public void testGetAllUsers(){
        List<User> users = session.selectList("com.pojo.UserMapper.selectUser");
        for (User u : users) {
            System.out.println(u);
        }
    }
    @Test
    public void testGetAllUsersCount(){
        Integer count = session.selectOne("com.pojo.UserMapper.selectUserCount");
        System.out.println(count);
    }
    @Test
    public void testGetUsersByPage1(){
        List<User> users = session.selectList("com.pojo.UserMapper.selectUsersByPage1");
        for (User u : users) {
            System.out.println(u);
        }
    }
    @Test
    public void testGetUsersByPage2(){
        List<User> users = session.selectList("com.pojo.UserMapper.selectUsersByPage2", 9);
        for (User u : users) {
            System.out.println(u);
        }
    }
    @Test
    public void testGetUsersByPage3(){
        Map<String, Integer> map = new HashMap<>();
        map.put("startIndex", 10);
        map.put("pageSize", 5);
        List<User> users = session.selectList("com.pojo.UserMapper.selectUsersByPage3", map);
        for (User u : users) {
            System.out.println(u);
        }
    }
    @Test
    public  void testSaveUser(){
        User u = new User();
        u.setUsername("lkt");
        u.setPassword("888888");
        u.setAddr("suzhou");
        u.setAge(20);
        int result = session.insert("com.pojo.UserMapper.saveUser", u);
        System.out.println(result);
    }
}

注意事項(xiàng)

• UserMapper的映射文件：

  • namespace和id在整個(gè)項(xiàng)目中突照，必須要保證唯一
  • namespace+id找到的是唯一的sql語句，標(biāo)簽可能不對應(yīng)洋魂，但是不影響執(zhí)行結(jié)果绷旗，但是還是需要規(guī)范各個(gè)標(biāo)簽

• TestUser.java

  • 創(chuàng)建SqlSession對象的時(shí)候，SqlSessionFactory對象的openSession（）方法不包含參數(shù)副砍，則使用事務(wù)手動提交衔肢，做完增刪改操作后，需要調(diào)用SqlSession對象的commit（）方法完成事務(wù)的提交豁翎。如果openSession（）方法包含有一個(gè)true角骤，代表自動提交生效，我們做完增刪改操作時(shí)候心剥，就完成了對應(yīng)的增刪改功能邦尊。openSession（）方法默認(rèn)的提交方式為手動提交
  • 該類活用了junit的生命周期方法，每個(gè)測試方法執(zhí)行之前都會調(diào)用標(biāo)注有@Before注解的setUp（）方法完成環(huán)境的準(zhǔn)備工作优烧，每個(gè)方法完成之后都自動的執(zhí)行標(biāo)注有@After注解的tearDown（）方法完成資源的釋放工作
  • SqlSession是mybatis中的核心對象蝉揍，使用該對象即可完成對于所有操作的crud功能，里面有對應(yīng)的方法畦娄，selectList（）又沾，查詢列表（集合）弊仪，selectOne（）查詢單個(gè)對象，insert（）杖刷，delete励饵，update（）分別對應(yīng)增刪改功能。這三個(gè)方法的返回值均為受影響的行數(shù)
  • 每次使用完SqlSession對象之后滑燃，使用close（）方法將SqlSession對象關(guān)閉役听，不建議關(guān)閉SqlSessionFactory對象
  • 關(guān)于傳遞參數(shù)
    • 傳遞單個(gè)值，sql語句里面的占位符可以任意寫
    • 多個(gè)值表窘，可以使用Map來傳值典予，map中的key要與sql語句中的占位符一致
    • 對象傳值，sql語句中的字段值與對象的屬性名一致
    • 零散值的傳遞乐严，可以使用兩種方式arg0熙参， arg1，...或者param1麦备，param2...