步骤1:先运行,看到成果,再学习
步骤2:模拟和排错
步骤3:在前一步的根底上进行
步骤4:配置文件Category.xml
步骤5:减少
步骤6:删除
步骤7:获取
步骤8:批改
步骤9:查问所有
步骤 1 : 先运行,看到成果,再学习
老规矩,先下载下载区(点击进入)的可运行我的项目,配置运行起来,确认可用之后,再学习做了哪些步骤以达到这样的成果。
步骤 2 : 模拟和排错
在确保可运行我的项目可能正确无误地运行之后,再严格照着教程的步骤,对代码模拟一遍。
模拟过程不免代码有出入,导致无奈失去冀望的运行后果,此时此刻通过比拟正确答案 ( 可运行我的项目 ) 和本人的代码,来定位问题所在。
采纳这种形式,学习有成果,排错有效率,能够较为显著地晋升学习速度,跨过学习路上的各个槛。
举荐应用diffmerge软件,进行文件夹比拟。把你本人做的我的项目文件夹,和我的可运行我的项目文件夹进行比拟。
这个软件很牛逼的,能够晓得文件夹里哪两个文件不对,并且很显著地标记进去
这里提供了绿色装置和应用教程:diffmerge 下载和应用教程
步骤 3 : 在前一步的根底上进行
这一个知识点解说通过Mybatis进行CRUD一套操作,建设在上一个知识点Mybatis 入门教程的根底上进行。
步骤 4 : 配置文件Category.xml
首先一次性批改配置文件Category.xml,提供CRUD对应的sql语句。
每个SQL如何应用在后续对应操作里一一解说。
<?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.how2java.pojo">
<insert id="addCategory" parameterType="Category">
insert into category_ ( name ) values (#{name})
</insert>
<delete id="deleteCategory" parameterType="Category">
delete from category_ where id= #{id}
</delete>
<select id="getCategory" parameterType="_int" resultType="Category">
select * from category_ where id= #{id}
</select>
<update id="updateCategory" parameterType="Category">
update category_ set name=#{name} where id=#{id}
</update>
<select id="listCategory" resultType="Category">
select * from category_
</select>
</mapper>
步骤 5 : 减少
运行之后,如图所示能够看到 通过Mybatis查问进去的数据里有新减少的Category
通过session.insert调用addCategory对应的SQL语句
Category c = new Category();
c.setName("新减少的Category");
session.insert("addCategory", c);
addCategory对应的插入sql语句,#{name}会主动获取c对象的name属性值
<insert id="addCategory" parameterType="Category" >
insert into category_ ( name ) values (#{name})
</insert>
- TestMybatis.java
- 代码片段1
package com.how2java;
import java.io.IOException;
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 com.how2java.pojo.Category;
public class TestMybatis {
public static void main(String[] args) throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = sqlSessionFactory.openSession();
Category c = new Category();
c.setName("新减少的Category");
session.insert("addCategory", c);
listAll(session);
session.commit();
session.close();
}
private static void listAll(SqlSession session) {
List<Category> cs = session.selectList("listCategory");
for (Category c : cs) {
System.out.println(c.getName());
}
}
}
<insert id="addCategory" parameterType="Category" >
insert into category_ ( name ) values (#{name})
</insert>
步骤 6 : 删除
删除id=6的对象
Category c = new Category();
c.setId(6);
session.delete("deleteCategory",c);
deleteCategory对应删除的sql语句
<delete id="deleteCategory" parameterType="Category" >
delete from category_ where id= #{id}
</delete>
- TestMybatis.java
- 代码片段1
package com.how2java;
import java.io.IOException;
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 com.how2java.pojo.Category;
public class TestMybatis {
public static void main(String[] args) throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = sqlSessionFactory.openSession();
Category c = new Category();
c.setId(6);
session.delete("deleteCategory", c);
listAll(session);
session.commit();
session.close();
}
private static void listAll(SqlSession session) {
List<Category> cs = session.selectList("listCategory");
for (Category c : cs) {
System.out.println(c.getName());
}
}
}
<delete id="deleteCategory" parameterType="Category" >
delete from category_ where id= #{id}
</delete>
步骤 7 : 获取
通过session.selectOne获取id=3的记录
Category c= session.selectOne("getCategory",3);
getCategory对应的sql语句:
<select id="getCategory" parameterType="_int" resultType="Category">
select * from category_ where id= #{id}
</select>
- TestMybatis.java
- 代码片段1
package com.how2java;
import java.io.IOException;
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 com.how2java.pojo.Category;
public class TestMybatis {
public static void main(String[] args) throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = sqlSessionFactory.openSession();
Category c = session.selectOne("getCategory", 3);
System.out.println(c.getName());
// listAll(session);
session.commit();
session.close();
}
private static void listAll(SqlSession session) {
List<Category> cs = session.selectList("listCategory");
for (Category c : cs) {
System.out.println(c.getName());
}
}
}
<select id="getCategory" parameterType="_int" resultType="Category">
select * from category_ where id= #{id}
</select>
步骤 8 : 批改
通过session.update进行批改
session.update("updateCategory",c);
updateCategory对应的sql语句:
<update id="updateCategory" parameterType="Category" >
update category_ set name=#{name} where id=#{id}
</update>
- TestMybatis.java
- 代码片段1
package com.how2java;
import java.io.IOException;
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 com.how2java.pojo.Category;
public class TestMybatis {
public static void main(String[] args) throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = sqlSessionFactory.openSession();
Category c = session.selectOne("getCategory", 3);
c.setName("批改了的Category名稱");
session.update("updateCategory", c);
listAll(session);
session.commit();
session.close();
}
private static void listAll(SqlSession session) {
List<Category> cs = session.selectList("listCategory");
for (Category c : cs) {
System.out.println(c.getName());
}
}
}
<update id="updateCategory" parameterType="Category" >
update category_ set name=#{name} where id=#{id}
</update>
步骤 9 : 查问所有
session.selectList执行查问语句
List<Category> cs = session.selectList("listCategory");
listCategory对应的sql语句
<select id="listCategory" resultType="Category">
select * from category_
</select>
- TestMybatis.java
- 代码片段1
package com.how2java;
import java.io.IOException;
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 com.how2java.pojo.Category;
public class TestMybatis {
public static void main(String[] args) throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = sqlSessionFactory.openSession();
listAll(session);
session.commit();
session.close();
}
private static void listAll(SqlSession session) {
List<Category> cs = session.selectList("listCategory");
for (Category c : cs) {
System.out.println(c.getName());
}
}
}
<select id="listCategory" resultType="Category">
select * from category_
</select>
更多内容,点击理解: https://how2j.cn/k/mybatis/mybatis-crud/1088.html