【MyBatis】Mybatis 注解开发
1. 常用的注解说明
@Insert:实现新增
@Update:实现更新
@Delete:实现删除
@Select:实现查询
@Result:实现结果集封装
@Results:可以与@Result 一起使用,封装多个结果集
@ResultMap:实现引用@Results 定义的封装
@One:实现一对一结果集封装
@Many:实现一对多结果集封装
@SelectProvider: 实现动态 SQL 映射
@CacheNamespace:实现注解二级缓存的使用
2. 通过注解实现基本CRUD操作
- 实体类(User)
package com.siyi.domain;
import java.io.Serializable;
import java.util.Date;
public class User implements Serializable {
private Integer id;
private String username;
private String address;
private String sex;
private Date birthday;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", address='" + address + '\'' +
", sex='" + sex + '\'' +
", birthday=" + birthday +
'}';
}
}
- 主配置文件SqlMapConfig.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>
<!-- 引入外部配置文件 -->
<properties resource="jdbcConfig.properties"/>
<!-- 配置别名 -->
<typeAliases>
<package name="com.siyi.domain"/>
</typeAliases>
<!-- 配置环境 -->
<environments default="mysql">
<environment id="mysql">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments>
<!-- 引入带有注解的DAO接口所在位置 -->
<mappers>
<package name="com.siyi.dao"/>
</mappers>
</configuration>
- 使用注解方式开发持久层接口
package com.siyi.dao;
import com.siyi.domain.User;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;
import java.util.List;
/**
* 在mybatis中针对,CRUD一共有四个注解
* @Select @Insert @Update @Delete
*/
public interface IUserDao {
/**
* 查询所有用户
* @return
*/
@Select("select * from user")
List<User> findAll();
/**
* 保存用户
* @param user
*/
@Insert("insert into user(username,address,sex,birthday) values(#{username},#{address},#{sex},#{birthday})")
public void saveUser(User user);
/**
* 更新用户
* @param user
*/
@Update("update user set username=#{username},sex=#{sex},address=#{address},birthday=#{birthday} where id=#{id}")
public void updateUser(User user);
/**
* 删除用户
* @param userId
*/
@Delete("delete from user where id=#{id} ")
public void deleteUser(Integer userId);
/**
* 根据id查询用户
* @param userId
* @return
*/
@Select("select * from user where id = #{id}")
public User findById(Integer userId);
/**
* 根据用户名称模糊查询
* @param username
* @return
*/
@Select("select * from user where username like #{username}")
public List<User> findUserByName(String username);
/**
* 查询总用户数量
* @return
*/
@Select("select count(*) from user")
public int findTotalUser();
}
- 测试
package com.siyi.test;
import com.siyi.dao.IUserDao;
import com.siyi.domain.User;
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 org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;
public class AnnotationCRUD {
private InputStream in;
private SqlSessionFactory factory;
private SqlSession session;
private IUserDao iUserDao;
@Before
public void init() throws IOException {
in = Resources.getResourceAsStream("SqlMapConfig.xml");
factory = new SqlSessionFactoryBuilder().build(in);
session = factory.openSession();
iUserDao = session.getMapper(IUserDao.class);
}
@After
public void destroy() throws IOException {
session.commit();
session.close();
in.close();
}
@Test
public void testSave(){
User user = new User();
user.setUsername("mybatis Annotation");
user.setAddress("北京市昌平区");
iUserDao.saveUser(user);
}
@Test
public void testUpdateUser(){
User user = new User();
user.setId(57);
user.setSex("男");
user.setAddress("北京市海淀区");
user.setUsername("mybatis annotation update");
user.setBirthday(new Date());
iUserDao.updateUser(user);
}
@Test
public void testDeleteUser(){
iUserDao.deleteUser(58);
}
@Test
public void testFindOne(){
User user = iUserDao.findById(57);
System.out.println(user);
}
@Test
public void testFindUserByName(){
List<User> users = iUserDao.findUserByName("%私忆%");
for (User user : users){
System.out.println(user);
}
}
@Test
public void testFindTotal(){
int totalUser = iUserDao.findTotalUser();
System.out.println(totalUser);
}
}
3. 使用注解实现一对多复杂关系映射
实现复杂关系映射之前我们可以在映射文件中通过配置来实现, 在使用注解开发时我们需要借助@Results 注解, @Result 注解, @One 注解, @Many 注解等等。
3.1 复杂关系映射的注解说明
@Results 注解
代替的是标签<resultMap>
该注解中可以使用单个@Result 注解,也可以使用@Result 集合
@Results({@Result(), @Result() })或@Results(@Result())
@Resutl 注解
代替了 <id>标签和<result>标签
@Result 中 属性介绍:
id 是否是主键字段
column 数据库的列名
property 需要装配的属性名
one 需要使用的@One 注解(@Result(one=@One())))
many 需要使用的@Many 注解(@Result(many=@many())))
@One 注解(一对一)
代替了<assocation>标签,是多表查询的关键,在注解中用来指定子查询返回单一对象。
@One 注解属性介绍:
select 指定用来多表查询的 sqlmapper
fetchType 会覆盖全局的配置参数 lazyLoadingEnabled。。
使用格式:
@Result(column=" ",property="",one=@One(select=""))
@Many 注解(多对一)
代替了<Collection>标签,是是多表查询的关键,在注解中用来指定子查询返回对象集合。
注意:聚集元素用来处理“一对多”的关系。需要指定映射的 Java 实体类的属性,属性的 javaType
(一般为 ArrayList)但是注解中可以不定义;
使用格式:
@Result(property="",column="",many=@Many(select=""))
3.2 使用注解实现一对一复杂关系映射及延迟加载
- 实体类(Account)
package com.siyi.domain;
public class Account {
private Integer id;
private Integer uid;
private Double money;
//多对一(mybatis中称之为1对1)的映射,一个账户只能属于一个用户
private User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Integer getUid() {
return uid;
}
public void setUid(Integer uid) {
this.uid = uid;
}
public Double getMoney() {
return money;
}
public void setMoney(Double money) {
this.money = money;
}
@Override
public String toString() {
return "Account{" +
"id=" + id +
", uid=" + uid +
", money=" + money +
'}';
}
}
- 持久层接口
package com.siyi.dao;
import com.siyi.domain.Account;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.mapping.FetchType;
import java.util.List;
public interface IAccountDao {
/**
* 查询所有账户并且获取每个账户所属的用户信息
* @return
*/
@Select("select * from account")
@Results(id = "accountMap",value = {
@Result(id=true,property = "id",column = "id"),
@Result(property = "uid",column = "uid"),
@Result(property = "money",column = "money"),
@Result(property = "user",column = "uid",one = @One(
select = "com.siyi.dao.IUserDao.findById",
fetchType = FetchType.EAGER
))
})
public List<Account> findAll();
/**
* 根据用户id查询账户信息
* @param userId
* @return
*/
@Select("select * from account where uid = #{userId}")
public List<Account> findAccountByUid(Integer userId);
}
- 测试类
package com.siyi.test;
import com.siyi.dao.IAccountDao;
import com.siyi.domain.Account;
import com.siyi.domain.User;
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 org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class AccountTest {
private InputStream in;
private SqlSessionFactory factory;
private SqlSession session;
private IAccountDao iAccountDao;
@Before
public void init() throws IOException {
in = Resources.getResourceAsStream("SqlMapConfig.xml");
factory = new SqlSessionFactoryBuilder().build(in);
session = factory.openSession();
iAccountDao = session.getMapper(IAccountDao.class);
}
@After
public void destroy() throws IOException {
session.commit();
session.close();
in.close();
}
@Test
public void testFindAll(){
List<Account> accounts = iAccountDao.findAll();
for(Account account : accounts){
System.out.println("------------------");
System.out.println(account);
System.out.println(account.getUser());
}
}
}
3.3 使用注解实现一对多复杂关系映射及延迟加载
- 实体类(User)
package com.siyi.domain;
import java.io.Serializable;
import java.util.Date;
import java.util.List;
public class User implements Serializable {
private Integer userId;
private String userName;
private String userAddress;
private String userSex;
private Date userBirthday;
private List<Account> accounts;
public List<Account> getAccounts() {
return accounts;
}
public void setAccounts(List<Account> accounts) {
this.accounts = accounts;
}
public Integer getUserId() {
return userId;
}
public void setUserId(Integer userId) {
this.userId = userId;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getUserAddress() {
return userAddress;
}
public void setUserAddress(String userAddress) {
this.userAddress = userAddress;
}
public String getUserSex() {
return userSex;
}
public void setUserSex(String userSex) {
this.userSex = userSex;
}
public Date getUserBirthday() {
return userBirthday;
}
public void setUserBirthday(Date userBirthday) {
this.userBirthday = userBirthday;
}
}
- 持久层接口
package com.siyi.dao;
import com.siyi.domain.User;
import org.apache.ibatis.annotations.*;
import org.apache.ibatis.mapping.FetchType;
import java.util.List;
/**
* 在mybatis中针对,CRUD一共有四个注解
* @Select @Insert @Update @Delete
*/
public interface IUserDao {
/**
* 查询所有用户
* @return
*/
@Select("select * from user")
@Results(id = "userMap",value = {
@Result(id=true,property = "userId",column = "id"),
@Result(property = "userName",column = "username"),
@Result(property = "userAddress",column = "address"),
@Result(property = "userSex",column = "sex"),
@Result(property = "userBirthday",column = "birthday"),
@Result(property = "accounts" , column = "id", many = @Many(
select = "com.siyi.dao.IAccountDao.findAccountByUid",
fetchType = FetchType.LAZY
))
})
/*@Many:
相当于<collection>的配置
select 属性:代表将要执行的 sql 语句
fetchType 属性:代表加载方式,一般如果要延迟加载都设置为 LAZY 的值*/
List<User> findAll();
/**
* 根据id查询用户
* @param userId
* @return
*/
@Select("select * from user where id = #{id}")
// @ResultMap(value = {"userMap"})
@ResultMap("userMap")
public User findById(Integer userId);
/**
* 根据用户名称模糊查询
* @param username
* @return
*/
@Select("select * from user where username like #{username}")
@ResultMap("userMap")
// @Select("select * from user where username like '%${value}%'")
public List<User> findUserByName(String username);
}
- 测试类
package com.siyi.test;
import com.siyi.dao.IUserDao;
import com.siyi.domain.User;
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 org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;
public class AnnotationCRUD {
private InputStream in;
private SqlSessionFactory factory;
private SqlSession session;
private IUserDao iUserDao;
@Before
public void init() throws IOException {
in = Resources.getResourceAsStream("SqlMapConfig.xml");
factory = new SqlSessionFactoryBuilder().build(in);
session = factory.openSession();
iUserDao = session.getMapper(IUserDao.class);
}
@After
public void destroy() throws IOException {
session.commit();
session.close();
in.close();
}
@Test
public void testFindAll(){
List<User> users = iUserDao.findAll();
for(User user : users){
System.out.println("---------------");
System.out.println(user);
System.out.println(user.getAccounts());
}
}
@Test
public void testFindOne(){
User user = iUserDao.findById(57);
System.out.println(user);
User user1 = iUserDao.findById(57);
System.out.println(user1);
System.out.println(user==user1);
}
@Test
public void testFindUserByName(){
List<User> users = iUserDao.findUserByName("%私忆%");
// List<User> users = iUserDao.findUserByName("私忆");
for (User user : users){
System.out.println(user);
}
}
}
4. 基于注解的二级缓存
- 在 主配置文件SqlMapConfig.xml中开启二级缓存支持
<?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>
<!-- 引入外部配置文件 -->
<properties resource="jdbcConfig.properties"/>
<!-- 配置二级缓存 -->
<settings>
<setting name="cacheEnabled" value="true"/>
</settings>
<!-- 配置别名 -->
<typeAliases>
<package name="com.siyi.domain"/>
</typeAliases>
<!-- 配置环境 -->
<environments default="mysql">
<environment id="mysql">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments>
<!-- 引入带有注解的DAO接口所在位置 -->
<mappers>
<package name="com.siyi.dao"/>
</mappers>
</configuration>
- 在持久层接口中使用注解配置二级缓存
package com.siyi.dao;
import com.siyi.domain.User;
import org.apache.ibatis.annotations.*;
import org.apache.ibatis.mapping.FetchType;
import java.util.List;
@CacheNamespace(blocking = true)//mybatis 基于注解方式实现配置二级缓存
public interface IUserDao {
....
}