MyBatis下載
MyBatis下載地址-
導(dǎo)入jar包
MyBatis的jar包只有一個, 但是它有一些依賴的jar包同樣需要導(dǎo)入:
libs.png
新建一個源文件夾: config
在config目錄中新建一個配置文件: Configuration.xml
<?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.jdbc.Driver" />
<property name="url" value="jdbc:mysql://localhost:3306/test" />
<property name="username" value="root" />
<property name="password" value="root" />
</dataSource>
</environment>
</environments>
<mappers>
//配置mapper的xml文件
</mappers>
</configuration>
創(chuàng)建一個pojo類, 與數(shù)據(jù)庫中的表對應(yīng)
在config目錄下創(chuàng)建一個專門存放mapper 的xml文件的文件夾:mapper
在mapper文件夾中新建Book.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.gongxm.gongxm.bean">
<select id="findBookById" parameterType="string" resultType="com.gongxm.bean.Book">
select * from books where id = #{id}
</select>
</mapper>
- 在Configuration.xml文件中加載Book.xml文件: 在mappers節(jié)點中配置:
<!-- resource是基于classpath查找的 -->
<mapper resource="mapper/Book.xml" />
-
創(chuàng)建完以上內(nèi)容后, 整體目錄結(jié)構(gòu)如下:
all.png 測試代碼
private SqlSessionFactory factory = null;
@Before
public void init() throws IOException {
// 1.創(chuàng)建SqlSessionFactoryBuilder對象
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
// 2.加載配置文件
InputStream is = Resources.getResourceAsStream("Configuration.xml");
// 3.創(chuàng)建SqlSessionFactory對象
factory = builder.build(is);
}
@Test
public void test1() throws IOException {
// 4.創(chuàng)建SqlSession對象
SqlSession session = factory.openSession();
// 5.使用SqlSession對象執(zhí)行查詢,得到結(jié)果
Book book = session.selectOne("findBookById", "a000Mm1WSnpoSjFIMVF4VE1LWEpKUT09");
// 6.顯示結(jié)果
System.out.println(book);
// 7.釋放資源
session.close();
}
- 查詢多條數(shù)據(jù): 在Book.xml文件中新增:
<!-- 查詢多條數(shù)據(jù)時, 返回類型只需要寫集合中的類型即可 -->
<select id="findBooksByName" parameterType="string" resultType="com.gongxm.bean.Book">
select * from books where book_name like #{name}
</select>
測試代碼:
SqlSession session = factory.openSession();
List<Book> list = session.selectList("findBooksByName","%修真%");
if(list!=null) {
for (Book book : list) {
System.out.println(book.getBook_name());
}
}
還可以這樣寫:
在Book.xml文件中的內(nèi)容:
<select id="findBooksByName" parameterType="string" resultType="com.gongxm.bean.Book">
select * from books where book_name like '%${value}%'
</select>
測試代碼:
SqlSession session = factory.openSession();
List<Book> list = session.selectList("findBooksByName","修真");
if(list!=null) {
for (Book book : list) {
System.out.println(book.getBook_name());
}
}
以上兩種方式的區(qū)別:
#{xxx} : 表示占位符, 名字可以隨便起
${value} : 表示字符串連接, 名字必須是value, 不能隨便起
- 插入一個數(shù)據(jù):
在Book.xml配置文件:
<insert id="addBook" parameterType="com.gongxm.bean.Book">
insert into books (id,book_name,book_link,author,category,collectStatus,cover,shortIntroduce,status)
values (#{id},#{book_name},#{book_link},#{author},#{category},#{collectStatus},#{cover},#{shortIntroduce},#{status})
</insert>
測試代碼:
Book book = new Book("99886128","gongxm", "http://www.gongxm.com/", "java入門", "java", 0, "http://www.gongxm.com/cover.jpg", "java入門必備神書!", "連載中");
SqlSession session = factory.openSession();
session.insert("addBook",book);
session.commit();//提交事務(wù)
session.close();
- 如果在插入數(shù)據(jù)時, 想要獲取到該條數(shù)據(jù)的ID, 可以在insert節(jié)點中增加以下內(nèi)容:
<!-- keyProperty對應(yīng)的是pojo對象中的屬性,
resultType對應(yīng)的是pojo對象中的屬性的類型,
order:
AFTER在插入數(shù)據(jù)之后執(zhí)行這個語句
BEFOR在插入數(shù)據(jù)之前執(zhí)行這個語句,例如使用UUID做id的時候
-->
<selectKey keyProperty="id" order="AFTER" resultType="int">
select last_insert_id() // 獲取到當(dāng)前事務(wù)中最后插入數(shù)據(jù)庫的ID
</selectKey>
- 刪除數(shù)據(jù)
在Book.xml配置文件:
<delete id="deleteBook" parameterType="string">
delete from books where id=#{id}
</delete>
測試代碼:
SqlSession session = factory.openSession();
session.delete("deleteBook", "99886128");
session.commit();//提交事務(wù)
session.close();
- 更新數(shù)據(jù)
在Book.xml配置文件:
<update id="updateBook" parameterType="com.gongxm.bean.Book">
update books set book_name=#{book_name},book_link=#{book_link},author=#{author},
category=#{category},collectStatus=#{collectStatus},cover=#{cover},
shortIntroduce=#{shortIntroduce},status=#{status} where id=#{id}
</update>
測試代碼:
Book book = new Book("99886128","gongxm2", "http://www.gongxm.com2/", "java入門2", "java2",1, "http://www.gongxm.com/cover2.jpg", "java入門必備神書2!", "完本");
SqlSession session = factory.openSession();
session.update("updateBook", book);
session.commit();//提交事務(wù)
session.close();
- Dao 的mapper代理開發(fā)方式
1.Book.xml中的namespace必須是接口的全類名:
<mapper namespace="com.gongxm.dao.BookDao">
2.id必須跟接口中的方法名相同:
<select id="findBookById" ...
3.parameterType要與接口中的參數(shù)類型一致
4.resultType要與接口中的返回值一致
代碼示例:
SqlSession session = factory.openSession();
BookDao dao = session.getMapper(BookDao.class);
Book book = dao.findBookById("99886128");
System.out.println(book);
