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MyBatis進修筆記(二)之聯系關系關系

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明天重要進修的聯系關系關系是一對一關系與一對多關系。

1、一對一關系

照樣經由過程例子來說明解釋。（一個老婆對應一個丈夫）。

1)數據庫信息

create table t_wife(
id int primary key auto_increment,
wife_name varchar(),
fk_husband_id int
);
create table t_husband(
id int primary key auto_increment,
husband_name varchar()
);
insert into t_husband values (null,'hello');
insert into t_wife values(null,'kitty',)

2）對應的JavaBean代碼

固然在數據庫裡只要一方設置裝備擺設的外鍵，然則這個一對一是雙向的關系。

HusbandBean.java

package com.cy.mybatis.beans;
import java.io.Serializable;
/**
* one to one
* @author acer
*
*/
public class HusbandBean implements Serializable{
private static final long serialVersionUID = L;
private Integer id;
private String name;
private WifeBean wife;
public HusbandBean() {
super();
}
public HusbandBean(Integer id, String name, WifeBean wife) {
super();
this.id = id;
this.name = name;
this.wife = wife;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public WifeBean getWife() {
return wife;
}
public void setWife(WifeBean wife) {
this.wife = wife;
}
@Override
public String toString() {
return "Husband [id=" + id + ", name=" + name + ", wife=" + wife + "]";
}
}

WifeBean.java

package com.cy.mybatis.beans;
import java.io.Serializable;
/**
* one to one
* @author acer
*
*/
public class WifeBean implements Serializable{
private static final long serialVersionUID = L;
private Integer id;
private String name;
private HusbandBean husband;
public WifeBean() {
super();
}
public WifeBean(Integer id, String name, HusbandBean husband) {
super();
this.id = id;
this.name = name;
this.husband = husband;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public HusbandBean getHusband() {
return husband;
}
public void setHusband(HusbandBean husband) {
this.husband = husband;
}
@Override
public String toString() {
return "Wife [id=" + id + ", name=" + name + ", husband=" + husband
+ "]";
}
}

3）接上去樹立兩個接口，HusbandMapper,WifeMapper.

HusbandMapper

package com.cy.mybatis.mapper;
import com.cy.mybatis.beans.HusbandBean;
public interface HusbandMapper {
/**
* 依據id查詢丈夫信息
* @param id
* @return
* @throws Exception
*/
public HusbandBean selectHusbandById (int id) throws Exception;
/**
* 依據id查詢丈夫與老婆信息
* @param id
* @return
* @throws Exception
*/
public HusbandBean selectHusbandAndWife(int id) throws Exception;
}

4）界說HusbandMapper.xml文件

<?xml version="." encoding="UTF-"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org/DTD Mapper ." "http://mybatis.org/dtd/mybatis--mapper.dtd">
<mapper namespace="com.cy.mybatis.mapper.HusbandMapper">
<resultMap type="HusbandBean" id="husbandAndWife">
<id property="id" column="id" javaType="java.lang.Integer"/>
<result property="name" column="name" javaType="java.lang.String"/>
<!-- association – 一個龐雜的類型聯系關系；很多成果將包成這類類型
嵌入成果映照 – 成果映照本身的聯系關系，或許參考一個
column="id" 這裡的id指的是在t_wife表來的主鍵id 
這個查詢老婆，所以在老婆mapper裡有個辦法 -->
<association property="wife" column="id" javaType="WifeBean" select="com.cy.mybatis.mapper.WifeMapper.selectWifeByHusbandId" ></association>
</resultMap>
<!-- resultType 前往類型 從這條語句中前往的希冀類型的類的完整限制名或別號
。-->
<select id="selectHusbandById" resultType="HusbandBean">
select * from t_husband where id=#{id}
</select> 
<!-- resultMap 定名援用內部的 resultMap。前往的是一個聚集。-->
<select id="selectHusbandAndWife" resultMap="husbandAndWife">
select * from t_husband where id=#{id}
</select>
</mapper>

在WifeMapper.xml裡有個辦法

<?xml version="." encoding="UTF-"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org/DTD Mapper ." "http://mybatis.org/dtd/mybatis--mapper.dtd">
<mapper namespace="com.cy.mybatis.mapper.WifeMapper">
<select id="selectWifeByHusbandId" resultType="WifeBean">
select * from t_wife where fk_husband_id = #{id}
</select> 
</mapper>

5）寫個完成

package com.cy.mybatis.service;
import org.apache.ibatis.session.SqlSession;
import com.cy.mybatis.beans.HusbandBean;
import com.cy.mybatis.mapper.HusbandMapper;
import com.cy.mybatis.tools.DBTools;
public class OneToOneService {
public static void main(String[] args) {
selectHusbandAndWife();
}
private static void selectHusbandAndWife() {
SqlSession session = DBTools.getSession();
HusbandMapper hm = session.getMapper(HusbandMapper.class);
try {
HusbandBean husband = hm.selectHusbandAndWife();
System.out.println(husband);
session.commit();
} catch (Exception e) {
e.printStackTrace();
}
}
}

留意：誰人對象類照樣前一章那樣寫的，就相當與在昨天的基本上樹立的。

留意：

mybatis現實是對XML停止操作，我們一切的辦法都直接界說在XML中，寫個接口只是為了更好的相符我們3層的思惟，假如不寫接口，直接經由過程session也能夠直接操作xml中的辦法，

XML中只需無方法，便可以應用，而挪用的方法就是：namespace+辦法名；

破例應用resultType時，必定要包管，你屬性名與字段名雷同；

假如不雷同，就應用resultMap 。

2、一對多關系

照樣經由過程例子來說明解釋。（一把鎖對應多把鑰匙）。

2.1）數據庫信息這裡沒有添加數據了，我們用批量添加數據

create table t_key(
id int primary key auto_increment,
key_name varchar(),
fk_lock_id int 
);
create table t_lock(
id int primary key auto_increment,
lock_name varchar()
);

2.2) 實體類

KeyBean.java

package com.cy.mybatis.beans;
import java.io.Serializable;
/**
* manyTOone
* 
*
*/
public class KeyBean implements Serializable {
private static final long serialVersionUID = L;
private Integer id;
private String key;
private LockBean lock;
public KeyBean() {
super();
}
public KeyBean(Integer id, String key, LockBean lock) {
super();
this.id = id;
this.key = key;
this.lock = lock;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getKey() {
return key;
}
public void setKey(String key) {
this.key = key;
}
public LockBean getLock() {
return lock;
}
public void setLock(LockBean lock) {
this.lock = lock;
}
@Override
public String toString() {
return "KeyBean [id=" + id + ", key=" + key + ", lock=" + lock + "]";
}
} 

LockBean.java

package com.cy.mybatis.beans;
import java.io.Serializable;
import java.util.List;
/**
* oneTOmany
* 
*
*/
public class LockBean implements Serializable{
private static final long serialVersionUID = L;
private Integer id;
private String lock;
private List<KeyBean> keys;
public LockBean() {
super();
}
public LockBean(Integer id, String lock, List<KeyBean> keys) {
super();
this.id = id;
this.lock = lock;
this.keys = keys;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getLock() {
return lock;
}
public void setLock(String lock) {
this.lock = lock;
}
public List<KeyBean> getKeys() {
return keys;
}
public void setKeys(List<KeyBean> keys) {
this.keys = keys;
}
@Override
public String toString() {
return "LockBean [id=" + id + ", keys=" + keys + ", lock=" + lock + "]";
}
}

2.3) 樹立接口

KeyMapper.java
package com.cy.mybatis.mapper;
import java.util.List;
import org.apache.ibatis.annotations.Param;
import com.cy.mybatis.beans.KeyBean;
public interface KeyMapper {
/**
* 批量添加鑰匙
* @return
* 倡導 如許應用 @Param("keys")
*/
public int batchSaveKeys(@Param("keys")List<KeyBean> keys);
} 

LockMapper.java

package com.cy.mybatis.mapper;
import org.apache.ibatis.annotations.Param;
import com.cy.mybatis.beans.LockBean;
public interface LockMapper {
/**
* 添加鎖
* @param lock
* @return
*/
public int saveLock(@Param("lock")LockBean lock);
/**
* 依據ID查詢鎖的材料
* @param id
* @return
*/
public LockBean findLockById(int id);
/**
* 依據ID查詢鎖與鑰匙的材料
* onemany
* @param id
* @return
*/
public LockBean findLockAndKeys(int id);
}

2.4) 樹立xml文件

KeyMapper.xml

<?xml version="." encoding="UTF-"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org/DTD Mapper ." "http://mybatis.org/dtd/mybatis--mapper.dtd">
<mapper namespace="com.cy.mybatis.mapper.KeyMapper">
<resultMap id="keyMap" type="KeyBean">
<id property="id" column="id" javaType="java.lang.Integer"/>
<result property="key" column="key_name" javaType="java.lang.String"/>
</resultMap>

<!--collection 為用於遍歷的元素（必選），支撐數組、List、Set -->
<!-- item 表現聚集中每個元素停止迭代時的別號. -->
<!--separator表現在每次停止迭代之間以甚麼符號作為分隔 符. -->
<insert id="batchSaveKeys">
insert into t_key values 
<foreach collection="keys" item="key" separator=",">
(null,#{key.key},#{key.lock.id})
</foreach>
</insert>
<select id="findKeysByLockId" resultMap="keyMap">
select * from t_key where fk_lock_id = #{id}
</select>
</mapper> 


LockMapper.xml

<?xml version="." encoding="UTF-"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org/DTD Mapper ." "http://mybatis.org/dtd/mybatis--mapper.dtd">
<mapper namespace="com.cy.mybatis.mapper.LockMapper">
<!--自界說前往類型 -->
<resultMap id="lockMap" type="LockBean">
<id property="id" column="id" javaType="java.lang.Integer"/>
<result property="lock" column="lock_name" javaType="java.lang.String"/>
</resultMap>
<!--自界說前往類型 -->
<resultMap id="lockAndKeysMap" type="LockBean">
<id property="id" column="id" javaType="java.lang.Integer"/>
<result property="lock" column="lock_name" javaType="java.lang.String"/>
<collection property="keys" column="id" select="com.cy.mybatis.mapper.KeyMapper.findKeysByLockId"></collection>
</resultMap>
<insert id="saveLock">
insert into t_lock values (null,#{lock.lock}) 
</insert>
<select id="findLockById" resultMap="lockMap">
select * from t_lock where id= #{id}
</select>
<select id="findLockAndKeys" resultMap="lockAndKeysMap">
select * from t_lock where id= #{id}
</select>
</mapper>

2.5 ）完成

package com.cy.mybatis.service;
import java.util.ArrayList;
import java.util.List;
import org.apache.ibatis.session.SqlSession;
import com.cy.mybatis.beans.KeyBean;
import com.cy.mybatis.beans.LockBean;
import com.cy.mybatis.mapper.KeyMapper;
import com.cy.mybatis.mapper.LockMapper;
import com.cy.mybatis.tools.DBTools;
public class OneToManyService {
public static void main(String[] args) {
// saveLock();
// batchSaveKeys();
findLockAndKeys();
}
private static void findLockAndKeys() {
SqlSession session = DBTools.getSession();
LockMapper lm = session.getMapper(LockMapper.class);
LockBean lock = lm.findLockAndKeys();
System.out.println(lock);
}
private static void batchSaveKeys() {
SqlSession session = DBTools.getSession();
LockMapper lm = session.getMapper(LockMapper.class);
KeyMapper km = session.getMapper(KeyMapper.class);
LockBean lock = lm.findLockById();
List<KeyBean> keys = new ArrayList<KeyBean>();
for(int i = ; i < ; i++){
KeyBean key = new KeyBean(null, "鑰匙"+i, lock);
keys.add(key);
}
km.batchSaveKeys(keys);
session.commit();
}
private static void saveLock() {
SqlSession session = DBTools.getSession();
LockMapper lm = session.getMapper(LockMapper.class);
LockBean lock = new LockBean(null, "鎖", null);
lm.saveLock(lock);
session.commit();
}
}

成果顯示：

三、批量操作與分頁

這裡就應用前一章的User.就寫出重要的代碼。

起首界說分頁對象。

package com.cy.mybatis.beans;
import java.util.List;
/**
* 界說一個分頁對象
* 
* @author
* 
*/
public class Pager {
private int pageNo;// 以後頁碼
private int pageTotal;// 總頁碼
private int rowsTotal;// 總條數
private int pageSize;// 每頁顯示條數
private List<Object> list;// 前往的數據聚集
public int getPageNo() {
return pageNo;
}
public void setPageNo(int pageNo) {
this.pageNo = pageNo;
}
public int getPageTotal() {
return pageTotal;
}
public void setPageTotal(int pageTotal) {
this.pageTotal = pageTotal;
}
public int getRowsTotal() {
return rowsTotal;
}
public void setRowsTotal(int rowsTotal) {
this.rowsTotal = rowsTotal;
pageTotal = rowsTotal % pageSize == ? rowsTotal / pageSize : rowsTotal / pageSize + ;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public List<?> getList() {
return list;
}
public void setList(List<Object> list) {
this.list = list;
}
@Override
public String toString() {
return "Pager [pageNo=" + pageNo + ", pageTotal=" + pageTotal
+ ", rowsTotal=" + rowsTotal + ", pageSize=" + pageSize
+ ", list=" + list + "]";
}
} 


UserMapper.java接口。

package com.cy.mybatis.mapper;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.annotations.Param;
import com.cy.mybatis.beans.UserBean;
public interface UserMapper {
/**
* 新增用戶
* @param user
* @return
* @throws Exception
*/
public int insertUser(@Param("user")UserBean user) throws Exception;
/**
* 修正用戶
* @param user
* @param id
* @return
* @throws Exception
*/
public int updateUser (@Param("u")UserBean user,@Param("id")int id) throws Exception;
/**
* 刪除用戶
* @param id
* @return
* @throws Exception
*/
public int deleteUser(int id) throws Exception;
/**
* 依據id查詢用戶信息
* @param id
* @return
* @throws Exception
*/
public UserBean selectUserById(int id) throws Exception;
/**
* 查詢一切的用戶信息
* @return
* @throws Exception
*/
public List<UserBean> selectAllUser() throws Exception;
/**
* 批量增長
* @param user
* @return
* @throws Exception
*/
public int batchInsertUser(@Param("users")List<UserBean> user) throws Exception;
/**
* 批量刪除
* @param list
* @return
* @throws Exception
*/
public int batchDeleteUser(@Param("list")List<Integer> list) throws Exception;
/**
* 分頁查詢數據
* @param parma
* @return
* @throws Exception
*/
public List<UserBean> pagerUser(Map<String, Object> parmas) throws Exception;
/**
* 
* 分頁統計數據
* @param parma
* @return
* @throws Exception
*/
public int countUser(Map<String, Object> parmas) throws Exception;
} 

xml文件

<?xml version="." encoding="UTF-"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org/DTD Mapper ." "http://mybatis.org/dtd/mybatis--mapper.dtd">
<mapper namespace="com.cy.mybatis.mapper.UserMapper">
<!-- 自界說前往成果集 -->
<resultMap id="userMap" type="UserBean">
<id property="id" column="id" javaType="java.lang.Integer"></id>
<result property="username" column="username" javaType="java.lang.String"></result>
<result property="password" column="password" javaType="java.lang.String"></result>
<result property="account" column="account" javaType="java.lang.Double"></result>
</resultMap>
<!-- 在各類標簽中的id屬性必需和接口中的辦法名雷同 ， id屬性值必需是獨一的，不克不及夠反復應用。parameterType屬性指明查詢時應用的參數類型，resultType屬性指明查詢前往的成果集類型--> 
<!-- useGeneratedKeys：（ 僅 對 insert 有 用 ） 這 會 告 訴 MyBatis 使 用 JDBC 的getGeneratedKeys 
辦法來掏出由數據（好比：像 MySQL 和 SQLServer 如許的數據庫治理體系的主動遞增字段）外部生成的主鍵。默許值： false。 --> 
<!--keyProperty： （僅對 insert有效）標志一個屬性， MyBatis 會經由過程 getGeneratedKeys或許經由過程 insert 語句的 selectKey 子元素設置它的值。默許：不設置。 -->
<!--#{}中的內容，為占位符，當參數為某個JavaBean時，表現放置該Bean對象的屬性值 -->
<insert id="insertUser" useGeneratedKeys="true" keyProperty="user.id">
insert into t_user (username,password,account) values (#{user.username},#{user.password},#{user.account})
</insert>
<update id="updateUser">
update t_user set username=#{u.username},password=#{u.password},account=#{u.account} where id=#{id}
</update>
<delete id="deleteUser" parameterType="int">
delete from t_user where id=#{id} 
</delete>
<select id="selectUserById" parameterType="int" resultMap="userMap">
select * from t_user where id=#{id}
</select>
<select id="selectAllUser" resultMap="userMap">
select * from t_user
</select>
<!-- 批量操作和foreach標簽 -->
<insert id="batchInsertUser" parameterType="java.util.List">
insert into t_user values 
<foreach collection="users" item="users" separator=",">
(null,#{users.username},#{users.password},#{users.account})
</foreach>
</insert>
<delete id="batchDeleteUser">
delete from t_user where id in (
<foreach collection="list" item="list" separator=",">
#{id}
</foreach>
)
</delete>
<!--collection 為用於遍歷的元素（必選），支撐數組、List、Set -->
<!-- item 表現聚集中每個元素停止迭代時的別號. -->
<!--separator表現在每次停止迭代之間以甚麼符號作為分隔 符. -->
<select id="pagerUser" parameterType="java.util.Map" resultMap="userMap">
select * from t_user where =
<if test="username!=null">
and username like '%${username}%'
</if>
limit ${index},${pageSize} 
</select>
<select id="countUser" parameterType="java.util.Map" resultType="int">
select count(*) from t_user where = 
<if test="username != null">
and username like '%${username}%' 
</if>
</select>
</mapper> 

#在生成SQL時，關於字符類型參數，會拼裝引號
$在生成SQL時，不會拼裝引號，可用於order by之類的參數拼裝

測試類

package com.cy.mybatis.service;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.session.SqlSession;
import com.cy.mybatis.beans.UserBean;
import com.cy.mybatis.tools.DBTools;
import com.cy.mybatis.mapper.UserMapper;
public class UserService {
/**
* @param args
*/
public static void main(String[] args) {
// insertUser();
// deleteUser();
// updateUser();
// selectUserById();
// selectAllUser();
// batchInsertUser();
// batchDeleteUser();
// countUser();
pagerUser();
}
private static void countUser() {
SqlSession session = DBTools.getSession();
UserMapper mapper = session.getMapper(UserMapper.class);
Map<String,Object> params = new HashMap<String,Object>();
params.put("username", "kitty");
int index = ;
params.put("index", index);//從第幾頁開端。mysql是從開端的
params.put("pageSize", );//每頁顯示的數據條數
int count;
try {
count = mapper.countUser(params);
System.out.println(count);
} catch (Exception e) {
e.printStackTrace();
}
}
private static void pagerUser() {
SqlSession session = DBTools.getSession();
UserMapper mapper = session.getMapper(UserMapper.class);
Map<String,Object> params = new HashMap<String,Object>();
params.put("username", "kitty");
params.put("index", );//從第幾頁開端。mysql是從開端的
params.put("pageSize", );//每頁顯示的數據條數
try {
List<UserBean> u = mapper.pagerUser(params);
for (UserBean userBean : u) {
System.out.println("--------"+userBean);
}
} catch (Exception e) {
e.printStackTrace();
}
}
private static void batchDeleteUser() {
SqlSession session = DBTools.getSession();
UserMapper mapper = session.getMapper(UserMapper.class);
List<Integer> ids = new ArrayList<Integer>();
for(int i = ; i < ; i ++){
ids.add(i);
}
try {
mapper.batchDeleteUser(ids);
session.commit();
} catch (Exception e) {
e.printStackTrace();
}
}
private static void batchInsertUser() {
SqlSession session = DBTools.getSession();
UserMapper mapper = session.getMapper(UserMapper.class);
List<UserBean> users = new ArrayList<UserBean>();
for(int i = ; i < ; i ++){
UserBean user = new UserBean("kitty"+i, "", .);
users.add(user);
}
try {
mapper.batchInsertUser(users);
session.commit();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 新增用戶
*/
private static void insertUser() {
SqlSession session = DBTools.getSession();
UserMapper mapper = session.getMapper(UserMapper.class);
UserBean user = new UserBean("懿", "", .);
try {
mapper.insertUser(user);
System.out.println(user.toString());
session.commit();
} catch (Exception e) {
e.printStackTrace();
session.rollback();
}
}
/**
* 刪除用戶
*/
private static void deleteUser(){
SqlSession session=DBTools.getSession();
UserMapper mapper=session.getMapper(UserMapper.class);
try {
mapper.deleteUser();
session.commit();
} catch (Exception e) {
e.printStackTrace();
session.rollback();
}
}
/**
* 修正用戶數據
*/
private static void updateUser(){
SqlSession session=DBTools.getSession();
UserMapper mapper=session.getMapper(UserMapper.class);
UserBean user =new UserBean("小明", "",.);
try {
mapper.updateUser(user, );
session.commit();
} catch (Exception e) {
e.printStackTrace();
session.rollback();
}
}
/**
* 依據id查詢用戶
*/
private static void selectUserById(){
SqlSession session=DBTools.getSession();
UserMapper mapper=session.getMapper(UserMapper.class);
try {
UserBean user= mapper.selectUserById();
System.out.println(user.toString());
session.commit();
} catch (Exception e) {
e.printStackTrace();
session.rollback();
}
}
/**
* 查詢一切的用戶
*/
private static void selectAllUser(){
SqlSession session=DBTools.getSession();
UserMapper mapper=session.getMapper(UserMapper.class);
try {
List<UserBean> user=mapper.selectAllUser();
System.out.println(user.toString());
session.commit();
} catch (Exception e) {
e.printStackTrace();
session.rollback();
}
} 
}

看一下項目標全體：

每件事都須要保持！