0. 描述:

關於是使用MyBatis多表之間的查詢操作，案例中表t_category 是描述書的分類，表t_Book是現有書表，兩個表之間通過cid欄位建立連線，本次通過兩種方式來實現 多對一的實現，關聯和分步來實現，實際開發中是分佈來實現的。

1. 表

CREATE TABLE `t_category`  (
  `cid` char(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `cname` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
  `desc` varchar(100) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
  PRIMARY KEY (`cid`) USING BTREE,
  UNIQUE INDEX `cname`(`cname`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

INSERT INTO `t_category` VALUES ('1', '程式設計', '程式設計分類');
INSERT INTO `t_category` VALUES ('3', '圖形 影象 多媒體', '圖形影象多媒體');
INSERT INTO `t_category` VALUES ('4', '作業系統/系統開發', '作業系統/系統開發');
INSERT INTO `t_category` VALUES ('458795C27E7346A8A5F1B942319297E0', '系統開發', '系統開發分類');
INSERT INTO `t_category` VALUES ('5', '資料庫', '資料庫');
INSERT INTO `t_category` VALUES ('57DE3C2DDA784B81844029A28217698C', 'Dreamweaver', 'Dreamweaver分類');
INSERT INTO `t_category` VALUES ('5F79D0D246AD4216AC04E9C5FAB3199E', 'Java Javascript', 'Java Javascript分類');
INSERT INTO `t_category` VALUES ('6', '網路與資料通訊', '網路與資料通訊!');
INSERT INTO `t_category` VALUES ('65830AB237EF428BAE9B7ADC78A8D1F6', 'Unix', 'Unix分類');
INSERT INTO `t_category` VALUES ('922E6E2DB04143D39C9DDB26365B3EE8', 'C C++ VC VC++', 'C C++ VC VC++分類');


CREATE TABLE `t_book`  (
  `bid` char(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `bname` varchar(200) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
  `author` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
  `price` decimal(8, 2) DEFAULT NULL,
  `press` varchar(100) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
  `cid` char(32) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
  PRIMARY KEY (`bid`) USING BTREE,
  INDEX `FK_t_book_t_category`(`cid`) USING BTREE,
  CONSTRAINT `FK_t_book_t_category` FOREIGN KEY (`cid`) REFERENCES `t_category` (`cid`) ON DELETE RESTRICT ON UPDATE RESTRICT
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;


INSERT INTO `t_book` VALUES ('52B0EDFF966E4A058BDA5B18EEC698C4', '亮劍Java Web專案開發案例導航(含DVD光碟1張)', '朱雪琴', 69.00, '電子工業出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('5315DA60D24042889400AD4C93A37501', 'Spring 3.x企業應用開發實戰(含CD光碟1張)', '陳雄華', 90.00, '電子工業出版社', '1');
INSERT INTO `t_book` VALUES ('56B1B7D8CD8740B098677C7216A673C4', '瘋狂 Java 程式設計師的基本修養（《瘋狂Java講義》最佳拍檔，掃清知識死角，夯實基本功）', '李剛', 59.00, '電子工業出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('57B6FF1B89C843C38BA39C717FA557D6', '了不起的Node.js: 將JavaScript進行到底（Web開發首選實時 跨多伺服器 高併發）', 'Guillermo Rauch', 79.00, '電子工業出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('5C68141786B84A4CB8929A2415040739', 'JavaScript高階程式設計(第3版)(JavaScript技術名著，國內JavasScript第一書，銷量超過8萬冊)', 'Nicholas C. Zakas', 99.00, '人民郵電出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('5EDB981339C342ED8DB17D5A198D50DC', 'Java程式效能優化', '葛一鳴', 59.00, '清華大學出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('A3D464D1D1344ED5983920B472826730', 'Java Web開發詳解：XML+DTD+XML Schema+XSLT+Servlet 3 0+JSP 2 2深入剖析與例項應用(含CD光碟1張)', '孫鑫', 119.00, '電子工業出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('A46A0F48A4F649AE9008B38EA48FAEBA', 'Java程式設計全能詞典(含DVD光碟2張)', '明日科技', 98.00, '電子工業出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('D0E69F85ACAB4C15BB40966E5AA545F1', 'Java併發程式設計實戰（第16屆Jolt大獎提名圖書，Java併發程式設計必讀佳作', 'Brian Goetz', 69.00, '機械工業出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('D2ABA8B06C524632846F27C34568F3CE', 'Java 經典例項', '達爾文', 98.00, '中國電力出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('D8723405BA054C13B52357B8F6AEEC24', '深入理解Java虛擬機器：JVM高階特性與最佳實踐（第2版）', '周志明', 79.00, '機械工業出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('DC36FD53A1514312A0A9ADD53A583886', 'JavaScript非同步程式設計：設計快速響應的網路應用【掌握JavaScript非同步程式設計必殺技，讓程式碼更具響應度！ 】', 'Trevor Burnham ', 32.00, '人民郵電出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('DCB64DF0084E486EBF173F729A3A630A', 'Java設計模式(第2版)', 'Steven John Metsker', 75.00, '電子工業出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('DCB64DF0084E486EBF173F798A3A630A', 'C++ Primer中文版（第5版）', '(美)李普曼 等', 128.00, '電子工業出版社', '922E6E2DB04143D39C9DDB26365B3EE8');
INSERT INTO `t_book` VALUES ('DEE7BDC7E0E343149E3C3601D2658171', '瘋狂HTML 5/CSS 3/JavaScript講義(含CD光碟1張)', '李剛', 69.00, '電子工業出版社', '1');
INSERT INTO `t_book` VALUES ('DF4E74EEE89B43229BB8212F0B858C38', '精通Hibernate：Java物件持久化技術詳解（第2版）(含光碟1張)', '孫衛琴', 75.00, '電子工業出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('EA695342393C4BE48B831FA5E6B0E5C4', '編寫可維護的JavaScript《JavaScript高階程式設計》作者Nicholas Zakas最新力作，構建編碼風格手冊，幫助開發團隊從“游擊隊”走向“正規軍”）', 'Nicholas C. Zakas', 55.00, '人民郵電出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('F0E34313BF304CCEBF198BD4E05307B8', 'jQuery Cookbook中文版（jQuery之父鼎力推薦，社群數十位專家傾情力作', 'jQuery社群專家組', 69.00, '人民郵電出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('F6162799E913423EA5CB57BEC65AB1E9', 'JUnit實戰(第2版)', '塔凱文', 79.00, '人民郵電出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('F693239BC3B3444C8538ABE7411BB38E', 'Java Web典型模組與專案實戰大全（配光碟）', '常建功', 99.50, '清華大學出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('F78C94641DB4475BBA1E72A07DF9B3AE', 'JAVA面向物件程式設計', '孫衛琴 ', 65.80, '電子工業出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('FC232CD9B6E6411BBBB1A5B781D2C3C9', 'Java與模式(含盤)（超多例項和習題，詳解設計原則與設計模式）', '閻巨集', 88.00, '電子工業出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('FEC3740CF30E442A94021911A25EF0D7', 'Spring攻略(第2版)(Spring攻略(第2版))', 'Gary Mak　Josh Long　Daniel Rubio', 128.00, '人民郵電出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
INSERT INTO `t_book` VALUES ('FFABBED1E5254BC0B2726EC4ED8ACCDA', '深入理解OSGi：Equinox原理、應用與最佳實踐（《深入理解Java虛擬機器》作者新作！全面解讀最新OSGi R5.0規範，深入講解OSGi原理和服務，以及Equinox框架的用法和原理）', '周志明', 79.00, '機械工業出版社', '5F79D0D246AD4216AC04E9C5FAB3199E');
 

2. 專案搭建

1. 匯入pom.xml

依賴的jar 表的外掛
 <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.4</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.0</version>
                <configuration>
                    <source>11</source>
                    <target>11</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>
 

2.Mybatis-config.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>

    <settings>
      <!--SQL日誌-->
      <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

   <environments default="development">
       <environment id="development">
           <!--事務管理器-->
           <transactionManager type="JDBC"/>
           <!--資料來源-->
           <dataSource type="POOLED">
               <property name="driver" value="com.mysql.jdbc.Driver"/>
               <property name="url" value="jdbc:mysql://127.0.0.1:3306/kdb2"/>
               <property name="username" value="root"/>
               <property name="password" value="root"/>
           </dataSource>
       </environment>
   </environments>
<!-- 對映程式碼存放區  -->
</configuration>
 

3. Mybatis 連線工具類

public class MyBatisUtil {
    private static final String resource = "mybatis-config.xml";
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    // ThreadLocal是一個和執行緒相關的容器，只要是在同一個執行緒中，獲取到的必定是同一個物件
    private static ThreadLocal<SqlSession> TL = new ThreadLocal<>();

    public static SqlSession openSession() {
        SqlSession sqlSession = TL.get();
        // 當前執行緒第一次呼叫該方法
        if (sqlSession == null) {
            sqlSession = sqlSessionFactory.openSession();
            TL.set(sqlSession);
        }
        return sqlSession;
    }
    public static void release(SqlSession sqlSession) {
        if (sqlSession != null) {
            sqlSession.close();
        }
    }
}

4. log4j 配置檔案

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
 
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
 
 <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
   <param name="Encoding" value="UTF-8" />
   <layout class="org.apache.log4j.PatternLayout">
    <param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m  (%F:%L) \n" />
   </layout>
 </appender>
 <logger name="java.sql">
   <level value="debug" />
 </logger>
 <logger name="org.apache.ibatis">
   <level value="info" />
 </logger>
 <root>
   <level value="debug" />
   <appender-ref ref="STDOUT" />
 </root>
</log4j:configuration>

5.domain

public class Book {
    private String bid;
    private String bname;
    private String author;
    private Double price;
    private String press;
    private String cid;
//  get/set method   and toString 
}

public class Category {
   private String cid;
   private String cname;
   private String desc;
//  get/set method   and toString 
}

1.關聯查詢的方式實現

1. 實體類 Book.java

2. 主配置檔案 Mybatis-config.xml

 </environments>
    <mappers>
        <mapper resource="cn/ccut/mapper/BookDao.xml"  ></mapper>
    </mappers>

3. 介面 IBookDao.java

4. BookDao.xml

<?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="cn.ccut.dao.IBookDao">
    <resultMap id="books"  type="cn.ccut.domain.Book">
        <id property="bid" column="bid"/>
        <result property="bname" column="bname"/>
        <result property="author" column="author"/>
        <result property="price" column="price"/>
        <result property="press" column="press"/>
        <result property="cid" column="cid"/>

<association property="category" column="cid" javaType="cn.ccut.domain.Category">
    <id property="cid" column="tcid"/>
    <result property="cname" column="tcname"></result>
    <result column="desc" property="desc"></result>
</association>
    </resultMap>
    <select id="selectQuery" resultMap="books">
select t1.cid tcid,t1.cname tcname,t1.desc,t.* from t_book  t join t_category t1 on t.cid=t1.cid and t.cid="5F79D0D246AD4216AC04E9C5FAB3199E"
    </select>
</mapper>

5. 測試

public class testS {
    @Test
    public void fun(){
        IBookDao mapper = MyBatisUtil.openSession().getMapper(IBookDao.class);
        System.out.println( mapper.selectQuery("1111"));
    }
}