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下面的例子讓新手看不錯。可以改進的一點是 1、不必建立 關聯對象實體，可以用map傳遞兩個id進去 2、文章的resultMap 繼承和 查詢配置 比較清楚，可以借鑒

????? mybatis3.0添加了association和collection標簽專門用于對多個相關實體類數據進行級聯查詢，但仍不支持多個相關實體類數據的級聯保存和級聯刪除操作。因此在進行實體類多對多映射表設計時，需要專門建立一個關聯對象類對相關實體類的關聯關系進行描述。下文將以“User”和“Group"兩個實體類之間的多對多關聯映射為例進行CRUD操作。

???? 建立user表，對應實體類"User"，建表語句如下：
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CREATE TABLE `user` (`id` int(11) NOT NULL auto_increment,`name` varchar(40) collate utf8_unicode_ci default NULL,`password` varchar(20) collate utf8_unicode_ci default NULL,`createtime` timestamp NULL default CURRENT_TIMESTAMP,PRIMARY KEY (`id`) )

建立group_info表，對應實體類"Group"，建表語句如下：

CREATE TABLE `group_info` (`id` int(11) NOT NULL auto_increment,`name` varchar(40) collate utf8_unicode_ci default NULL,`createdate` timestamp NULL default CURRENT_TIMESTAMP,`state` int(1) default '0' COMMENT '0:可見;1:不可見',PRIMARY KEY (`id`) )

建立user_group表，對應實體類"UserGroupLink"(該類為User和Group兩個實體類之間的關系描述)，建表語句如下：

CREATE TABLE `user_group` (`user_id` int(11) default NULL,`group_id` int(11) default NULL,`createdate` timestamp NULL default CURRENT_TIMESTAMP,KEY `FK_user_group_user_id` (`user_id`),KEY `FK_user_group_group_id` (`group_id`),CONSTRAINT `FK_user_group_group_id` FOREIGN KEY (`group_id`) REFERENCES `group_info` (`id`),CONSTRAINT `FK_user_group_user_id` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`) )

建立實體類User，代碼如下：

package com.xxt.ibatis.dbcp.domain;import java.util.Date; import java.util.List;/*** @describe: User實體類* @author: Nirvana* @version: V1.0 2011-3-11下午06:06:49 create*/public class User {private long id;private String name;private String password;private Date createTime;private List<Group> group;public Date getCreateTime() {return createTime;}public void setCreateTime(Date createTime) {this.createTime = createTime;}public long getId() {return id;}public void setId(long id) {this.id = id;}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 List<Group> getGroup() {return group;}public void setGroup(List<Group> group) {this.group = group;} }

建立實體類Group,代碼如下：

package com.xxt.ibatis.dbcp.domain;import java.util.Date; import java.util.List;/*** @describe: Group實體類* @author: Nirvana* @version: V1.0 2011-3-7下午08:10:29 create*/ public class Group {private long id;private String name; // 組名private Date createTime;private int state; // 0可見狀態 1不可見狀態private List<User> user;public Date getCreateTime() {return createTime;}public void setCreateTime(Date createTime) {this.createTime = createTime;}public long getId() {return id;}public void setId(long id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getState() {return state;}public void setState(int state) {this.state = state;}public List<User> getUser() {return user;}public void setUser(List<User> user) {this.user = user;}}

建立實體類UserGroupLink，用于描述User和Group之間的對應關系，代碼如下：

package com.xxt.ibatis.dbcp.domain;import java.util.Date;/*** @describe: 描述User和Group之間的映射關系* @author: Nirvana* @version: V1.0 2011-3-11下午02:57:52 create*/ public class UserGroupLink {private User user;private Group group;private Date createTime;public Date getCreateTime() {return createTime;}public void setCreateTime(Date createTime) {this.createTime = createTime;}public Group getGroup() {return group;}public void setGroup(Group group) {this.group = group;}public User getUser() {return user;}public void setUser(User user) {this.user = user;} }

建立user實體類的映射文件user.map.xml，代碼如下：

<?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.xxt.ibatis.dbcp.domain.User"><resultMap type="User" id="userMap"><id property="id" column="id" /><result property="name" column="name" /><result property="password" column="password" /><result property="createTime" column="createtime" /></resultMap><resultMap type="User" id="userGroupMap" extends="userMap"><collection property="groups" ofType="Group"><id property="id" column="goupId" /><result property="name" column="groupName" /><result property="state" column="state" /><result property="createTime" column="groupCreateTime" /></collection></resultMap><!-- 根據user表中的id查詢用戶信息 --><select id="selectUser" parameterType="long" resultMap="userMap">select * from user where id = #{id}</select><!-- 根據user表中的id查詢用戶和組信息 --><select id="selectUserGroup" parameterType="long"resultMap="userGroupMap">select u.id,u.name,u.password,u.createtime, gi.id asgoupId,gi.name as groupName, gi.createdate as groupCreateTime,gi.state from user u left join user_group ug on u.id=ug.user_idleft join group_info gi on ug.group_id=gi.id where u.id = #{id}</select><!-- 插入用戶信息 --><insert id="saveUser" parameterType="User" keyProperty="id"useGeneratedKeys="true">insert into user(name,password) values(#{name},#{password})</insert><!-- 保存用戶和組之間的關系信息 --><insert id="saveRelativity" parameterType="UserGroupLink">insert into user_group(user_id,group_id)values(#{user.id},#{group.id})</insert><select id="selectAllUser" resultMap="userMap">select * from user</select></mapper>

建立group實體類的映射文件group.map.xml，代碼如下:

<?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.xxt.ibatis.dbcp.domain.Group"><resultMap type="Group" id="groupMap"><id property="id" column="id" /><result property="name" column="name" /><result property="createTime" column="createdate" /></resultMap><resultMap type="Group" id="groupUserMap" extends="groupMap"><collection property="users" ofType="User"><id property="id" column="userId" /><result property="name" column="userName" /><result property="password" column="password" /><result property="createTime" column="userCreateTime" /></collection></resultMap><!-- 根據Group表中的id或name查詢組信息和組內用戶信息 --><select id="selectGroupUser" parameterType="Group"resultMap="groupUserMap">select u.id as userId,u.name as userName,u.password,u.createtime as userCreateTime,gi.id,gi.name,gi.createdate,gi.state from group_info gi leftjoin user_group ug on gi.id=ug.group_id left join user u onug.user_id=u.id<where><!--當id為初始值0，不再使用id作為查詢條件 --><if test="id != 0 ">gi.id=#{id}</if><!-- 當name為空或為空串時，不再使用name作為查詢條件 --><if test="name != null and name != ''">or gi.name = #{name}</if></where></select><!-- 根據id查詢group組信息 --><select id="selectGroup" parameterType="Date"resultMap="groupMap">select * from group_info where id=#{group_id}</select><!--根據name查詢group組信息 --><select id="getGroupByName" parameterType="String"resultMap="groupMap">select * from group_info where name=#{name}</select><!-- 插入組信息 --><insert id="saveGroup" parameterType="Group" keyProperty="id"useGeneratedKeys="true">insert into group_info(name) values(#{name})</insert><!-- 刪除組與組內成員之間的對應關系 --><delete id="deleteGroupUser" parameterType="UserGroupLink">delete from user_group<where><if test="user.id != 0">user_id = #{user.id}</if><if test="group.id != 0">and group_id = #{group.id}</if></where></delete><!--根據組id或者組name刪除組信息 --><delete id="deleteGroup" parameterType="Group">delete from group_info<where><if test="id!=0">id=#{id}</if><if test="name!=null || name!=''">and name=#{name}</if></where></delete><!-- 更新根據組id或者組name更新組狀態 --><update id="updateGroupState" parameterType="Group">update group_info set state=#{state}<where><if test="id!=0">id=#{id}</if><if test="name!=null || name!=''">and name=#{name}</if></where></update> </mapper>

建立ibatis總配置文件salMapConfig.xml,代碼如下：

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<?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><properties resource="jdbc.properties" /><typeAliases><typeAlias type="com.xxt.ibatis.dbcp.domain.User" alias="User" /><typeAlias type="com.xxt.ibatis.dbcp.domain.Group"alias="Group" /><typeAlias type="com.xxt.ibatis.dbcp.domain.UserGroupLink"alias="UserGroupLink" /></typeAliases><environments default="development"><environment id="development"><transactionManager type="JDBC" /><dataSource type="UNPOOLED"><property name="driver" value="${driver}" /><property name="url" value="${url}" /><property name="username" value="${username}" /><property name="password" value="${password}" /></dataSource></environment></environments><mappers><mapper resource="com/xxt/ibatis/dbcp/domain/user.map.xml" /><mapper resource="com/xxt/ibatis/dbcp/domain/group.map.xml" /></mappers> </configuration>

測試用例，代碼如下：

package com.xxt.ibatis.dbcp.test;import java.io.Reader; import java.text.SimpleDateFormat; import java.util.List;import org.junit.AfterClass; import org.junit.BeforeClass; import org.junit.Test;import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder;import com.xxt.ibatis.dbcp.domain.Group; import com.xxt.ibatis.dbcp.domain.User; import com.xxt.ibatis.dbcp.domain.UserGroupLink;/*** @describe: 測試用例* @author: Nirvana* @version: V1.0 2011-3-4下午03:21:17 create*/ public class IbatisUserTest {private final static String IBATIS_CONFIG_XML = "sqlMapConfig.xml"; private static SqlSession session;private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd k:mm:ss");@BeforeClasspublic static void setUpBeforeClass() throws Exception {Reader reader = Resources.getResourceAsReader(IBATIS_CONFIG_XML); //讀取ibatis配置文件SqlSessionFactory sqlMapper = new SqlSessionFactoryBuilder().build(reader);session = sqlMapper.openSession(true);session.commit(false); //將默認提交事務屬性設置為否}//保存用戶信息@Testpublic void saveUserTest(){User user = new User();user.setName("張三");user.setPassword("123456");session.insert("com.xxt.ibatis.dbcp.domain.User.saveUser", user);}//獲取用戶信息@Testpublic void getUserTest(){User user = (User) session.selectOne("com.xxt.ibatis.dbcp.domain.User.selectUser", 1L);System.out.println("用戶名： "+user.getName());System.out.println("用戶密碼: "+user.getPassword());System.out.println("用戶創建日期："+sdf.format(user.getCreateTime()));}//獲取用戶和用戶所在組信息@Testpublic void getUserAndGroupTest(){User user = (User)session.selectOne("com.xxt.ibatis.dbcp.domain.User.selectUserGroup", 4L);System.out.println(user.getName() +"所屬組信息:");for(Group group : user.getGroups() ){System.out.println(" 組名:"+group.getName()+"，組創建時間:"+sdf.format(group.getCreateTime()));}}//保存用戶和用戶所在組信息//當用戶所在組不存在時，創建該組，并生成映射關系@Testpublic void saveUserAndGroupTest(){User user = new User();user.setName("無常鬼");user.setPassword("wuchang");session.insert("com.xxt.ibatis.dbcp.domain.User.saveUser", user);Group groupImpl = (Group)session.selectOne("com.xxt.ibatis.dbcp.domain.Group.getGroupByName","用戶組4");//獲取組實例UserGroupLink ugl = new UserGroupLink();//聲明User和Group實體間映射關系實例//查詢到的組實例為空時的邏輯處理if(groupImpl == null){Group group = new Group();group.setName("用戶組4");session.insert("com.xxt.ibatis.dbcp.domain.Group.saveGroup", group);//持久化創建好的組實例//設置映射關系實例相關的屬性ugl.setUser(user);ugl.setGroup(group);session.insert("com.xxt.ibatis.dbcp.domain.User.saveRelativity",ugl);//持久化映射關系實力}else{ugl.setGroup(groupImpl);ugl.setUser(user);session.insert("com.xxt.ibatis.dbcp.domain.User.saveRelativity",ugl);}}//刪除組信息的同時，取消組內所有的成員與該組的關聯關系@Testpublic void deleteGroupTest(){Group group = new Group();//group.setId(1L); //以組id作為查詢條件group.setName("用戶組1"); //以組name作為查詢條件Group groupImpl = (Group)session.selectOne("com.xxt.ibatis.dbcp.domain.Group.selectGroupUser",group);//獲取組實例//組實例存在時if(groupImpl != null){List<User> users = groupImpl.getUsers();//查看用戶組1中是否存在用戶if(users != null && users.size() > 0){//存在用戶時，先刪除組與用戶的對應關系UserGroupLink ugl = new UserGroupLink();for(User user : users){ugl.setUser(user);ugl.setGroup(groupImpl);session.delete("com.xxt.ibatis.dbcp.domain.Group.deleteGroupUser",ugl );} }//刪除組信息session.delete("com.xxt.ibatis.dbcp.domain.Group.deleteGroup", groupImpl);}else{throw new RuntimeException("查詢的組不存在!!");}}//更新組狀態，當組狀態由可見狀態變成不可見時，取消該組下的用戶與該組的映射關系@Testpublic void updateGroupStateTest(){Group group = new Group();group.setName("用戶組2");Group groupImpl = (Group) session.selectOne("com.xxt.ibatis.dbcp.domain.Group.selectGroupUser",group);if(groupImpl != null){int state = groupImpl.getState() == 1 ? 0 : 1;//組狀態由0變成1時，即由可見變為不可見if(state == 1){List<User> users = groupImpl.getUsers();//查看用戶組2中是否存在用戶if(users != null && users.size() > 0){//存在用戶時，刪除組與用戶的對應關系UserGroupLink ugl = new UserGroupLink();for(User user : users){ugl.setUser(user);ugl.setGroup(groupImpl);session.delete("com.xxt.ibatis.dbcp.domain.Group.deleteGroupUser",ugl );} }} //更新組狀態groupImpl.setState(state);}else{throw new RuntimeException("查詢的組不存在!!");}}@AfterClasspublic static void tearDownAfterClass() throws Exception {if(session != null){session.commit(); //提交事務session.close(); //關閉連接}} }

轉載于:https://my.oschina.net/baochanghong/blog/519724

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