利用Mybatis对数据库进行增删改查操作
实现根据用户名模糊查询用户
先来了解一下 #{}和${}的使用
#{}表示一个占位符号，通过#{}可以实现preparedStatement向占位符中设置值，自动进行java类型和jdbc类型转换。#{}可以有效防止sql注入。 #{}可以接收简单类型值或pojo属性值。 如果parameterType传输单个简单类型值，#{}括号中可以是value或其它名称。#{}默认加单引号
\
${}表示拼接sql串，通过${}可以将parameterType 传入的内容拼接在sql中且不进行jdbc类型转换， 可以接收简单类型值或pojo属性值，如果parameterType传输单个简单类型值，∗∗ 可 以 接 收 简 单 类 型 值 或 p o j o 属 性 值 ， 如 果 p a r a m e t e r T y p e 传 输 单 个 简 单 类 型 值 ， ∗ ∗ {}括号中只能是value**。${}默认不加单引号
1.查询sql：
SELECT * FROM user WHERE username LIKE ‘%王%’
2.在User.xml配置文件中添加如下内容：
<select id="queryUserByUsername2" parameterType="string"
resultType="cn.itcast.mybatis.pojo.User">
SELECT * FROM `user` WHERE username LIKE '%${value}%'
select>- 测试程序
MybatisTest中添加测试方法如下：
@Test
public void testQueryUserByUsername2() throws Exception {
// 4. 创建SqlSession对象
SqlSession sqlSession = sqlSessionFactory.openSession();
// 5. 执行SqlSession对象执行查询，获取结果User
// 查询多条数据使用selectList方法
ListparameterType和resultType的使用
parameterType：
指定输入参数类型，mybatis通过ognl从输入对象中获取参数值拼接在sql中。
resultType：
指定输出结果类型，mybatis将sql查询结果的一行记录数据映射为resultType指定类型的对象。如果有多条数据，则分别进行映射，并把对象放到容器List中
selectOne和selectList的使用
selectOne:查询一条记录
User user = openSession.selectOne("queryUserById", 1);selectList可以查询一条或多条记录。
List user = openSession.selectList("queryUserByName", "hexiang"); 记住：查询操作openSession不需要提交事务，而如果是增删改需要openSession.commit()来提交事务
mysql自增主键返回
LAST_INSERT_ID():是mysql的函数，返回auto_increment自增列新记录id值。
<insert id="saveUser" parameterType="cn.itcast.mybatis.pojo.User">
<selectKey keyColumn="id" keyProperty="id" order="AFTER"
resultType="int">
SELECT LAST_INSERT_ID()
selectKey>
INSERT INTO `user`
(username,birthday,sex,address) VALUES
(#{username},#{birthday},#{sex},#{address})
insert>
Mysql使用 uuid实现主键
需要增加通过select uuid()得到uuid值,注意这里使用的order是“BEFORE”
<insert id="saveUser" parameterType="cn.itcast.mybatis.pojo.User">
<selectKey keyColumn="id" keyProperty="id" order="BEFORE"
resultType="string">
SELECT LAST_INSERT_ID()
selectKey>
INSERT INTO `user`
(username,birthday,sex,address) VALUES
(#{username},#{birthday},#{sex},#{address})
insert>
看到UUID和自增长的id想必大家想了解它们的区别？
uuid是按照字符型存储(可以用string类型)，正常自增长用的id是int类型占四个字节，当数据量非常大的时候就可以提现出id和uuid之间的区别，假设用500万个数据来模拟的话，id可以相对uuid节省2.5G空间,详细区别，可以问度娘.
增删改查代码：
新建的项目中的列表用到的文件是User.java(目标对象)、TestDemo1.java(测试类)、SqlMapConfig.xml(数据库连接池配置)、User.xml(数据库增删查改配置)、jdbc.properties(配置信息：账户密码等)、log4j.properties(控制台打印日志)：
目标对象：
User.java
package com.firtDay.sqlMapconFig;
import java.io.Serializable;
public class User implements Serializable {
@Override
public String toString() {
return "User [_name=" + _name + ", _money=" + _money + "]";
}
private Integer id;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
private String _name;
private int _money;
public String get_name() {
return _name;
}
public void set_name(String _name) {
this._name = _name;
}
public int get_money() {
return _money;
}
public void set_money(int _money) {
this._money = _money;
}
}
TestDemo1.java
package com.test;
import java.io.InputStream;
import java.util.List;
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.Before;
import org.junit.Test;
import com.firtDay.sqlMapconFig.User;
public class TestDemo1 {
private SqlSessionFactory sqlSessionFactory=null;
@Before
public void testDemo() throws Exception{
// 1. 创建SqlSessionFactoryBuilder对象
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
String url="SqlMapConfig.xml";
InputStream resource = Resources.getResourceAsStream(url);
this.sqlSessionFactory = sqlSessionFactoryBuilder.build(resource);
}
@Test
public void testDemo2(){
SqlSession openSession = sqlSessionFactory.openSession();
User user = openSession.selectOne("queryUserById", 1);
System.out.println(user);
openSession.close();
}
@Test
public void testDemo3(){
SqlSession openSession = sqlSessionFactory.openSession();
List user = openSession.selectList("queryUserByName", "hexiang");
for (User user2 : user) {
System.out.println(user2);
}
openSession.close();
}
@Test
public void testDemo4(){
SqlSession openSession = sqlSessionFactory.openSession();
User user = new User();
user.set_name("hha");
user.set_money(1000);
int insert = openSession.insert("addUser", user);//返回值为影响的行数
System.out.println(insert);
openSession.commit();//需要提交事务
System.out.println("id:"+user.getId());
openSession.close();
}
//更新数据
@Test
public void testDemo5(){
SqlSession openSession = sqlSessionFactory.openSession();
User user = new User();
user.setId(9);
user.set_name("111xxxoooo");
user.set_money(1000);
int update = openSession.update("updateUser", user);
openSession.commit();
openSession.close();
}
//删除数据
@Test
public void testDemo6(){
SqlSession openSession = sqlSessionFactory.openSession();
User user = new User();
openSession.update("deleteUserById", 9);
openSession.commit();
openSession.close();
}
}
SqlMapConfig.xml
<configuration>
<properties resource="jdbc.properties">properties>
<typeAliases>
<package name="com.firtDay.sqlMapconFig"/>
typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<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="User.xml"/>
<mapper resource="mapper.xml"/>
mappers>
configuration>
User.xml
<mapper namespace="test">
<select id="queryUserById" parameterType="Integer"
resultType="com.firtDay.sqlMapconFig.User">
SELECT * FROM `t_user` WHERE id = #{id}
select>
<select id="queryUserByName" parameterType="String"
resultType="com.firtDay.sqlMapconFig.User">
SELECT * FROM `t_user` WHERE _name like '%${value}%'
select>
<insert id="addUser" parameterType="com.firtDay.sqlMapconFig.User"
>
<selectKey keyProperty="id" resultType="Integer" order="AFTER">
select LAST_INSERT_ID()
selectKey>
INSERT INTO t_user(_name,_money) values (#{_name},#{_money})
insert>
<update id="updateUser" parameterType="com.firtDay.sqlMapconFig.User">
UPDATE t_user set _name = #{_name},_money = #{_money} WHERE id = #{id}
update>
<delete id="deleteUserById" parameterType="Integer">
delete from t_user where id = #{id}
delete>
mapper>
TestDemo1.java
package com.test;
import java.io.InputStream;
import java.util.List;
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.Before;
import org.junit.Test;
import com.firtDay.sqlMapconFig.User;
public class TestDemo1 {
private SqlSessionFactory sqlSessionFactory=null;
@Before
public void testDemo() throws Exception{
// 1. 创建SqlSessionFactoryBuilder对象
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
String url="SqlMapConfig.xml";
InputStream resource = Resources.getResourceAsStream(url);
this.sqlSessionFactory = sqlSessionFactoryBuilder.build(resource);
}
@Test
public void testDemo2(){
SqlSession openSession = sqlSessionFactory.openSession();
User user = openSession.selectOne("queryUserById", 1);
System.out.println(user);
openSession.close();
}
@Test
public void testDemo3(){
SqlSession openSession = sqlSessionFactory.openSession();
List user = openSession.selectList("queryUserByName", "hexiang");
for (User user2 : user) {
System.out.println(user2);
}
openSession.close();
}
@Test
public void testDemo4(){
SqlSession openSession = sqlSessionFactory.openSession();
User user = new User();
user.set_name("hha");
user.set_money(1000);
int insert = openSession.insert("addUser", user);//返回值为影响的行数
System.out.println(insert);
openSession.commit();//需要提交事务
System.out.println("id:"+user.getId());
openSession.close();
}
//更新数据
@Test
public void testDemo5(){
SqlSession openSession = sqlSessionFactory.openSession();
User user = new User();
user.setId(9);
user.set_name("111xxxoooo");
user.set_money(1000);
int update = openSession.update("updateUser", user);
openSession.commit();
openSession.close();
}
//删除数据
@Test
public void testDemo6(){
SqlSession openSession = sqlSessionFactory.openSession();
User user = new User();
openSession.update("deleteUserById", 9);
openSession.commit();
openSession.close();
}
}