步骤1:先运行，看到成果，再学习
步骤2:模拟和排错
步骤3:减少100条catgory数据
步骤4:批改Category.xml
步骤5:测试
步骤6:注解形式
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 : 减少100条catgory数据
为了察看分页查问的成果，把分类表里的数据都删除掉，而后新增100个数据
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();
List<Category> cs = session.selectList("listCategory");
for (Category c : cs) {
session.delete("deleteCategory", c);
}
for (int i = 0; i < 100; i++) {
Category c = new Category();
c.setName("category name " + i);
session.insert("addCategory", c);
}
List<Category> cs2 = session.selectList("listCategory");
for (Category c : cs2) {
System.out.println(c.getName());
}
session.commit();
session.close();
}
}步骤 4 : 批改Category.xml
新增limit
<?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_
<if test="start!=null and count!=null">
limit #{start},#{count}
</if>
</select>
</mapper>步骤 5 : 测试
用注解形式再做一遍
注： start是指从第0个开始，如果是第二页，那么就是第5个开始。
注： count参数是指每页有5条数据
- CategoryMapper.java
- TestMybatis.java
package com.how2java.mapper;
import java.util.List;
import org.apache.ibatis.annotations.Many;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import com.how2java.pojo.Category;
public interface CategoryMapper {
public List<Category> list();
public List<Category> listByPage(@Param("start") int start, @Param("count")int count);
}
package com.how2java;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
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.mapper.CategoryMapper;
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();
// xmlWay(session);
annotationWay(session);
session.commit();
session.close();
}
private static void xmlWay(SqlSession session) {
Map<String,Object> params = new HashMap<>();
params.put("start", 0);
params.put("count", 5);
List<Category> cs =session.selectList("listCategory", params);
for (Category c : cs) {
System.out.println(c);
}
}
private static void annotationWay(SqlSession session) {
CategoryMapper mapper = session.getMapper(CategoryMapper.class);
List<Category> cs =mapper.listByPage(0, 5);
for (Category c : cs) {
System.out.println(c);
}
}
}步骤 6 : 注解形式
- CategoryMapper.java
- TestMybatis.java
package com.how2java.mapper;
import java.util.List;
import org.apache.ibatis.annotations.Many;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import com.how2java.pojo.Category;
public interface CategoryMapper {
@Select(" select * from category_ ")
@Results({@Result(property = "products", javaType = List.class, column = "id",
many = @Many(select = "com.how2java.mapper.ProductMapper.listByCategory"))})
public List<Category> list();
@Select(" select * from category_ limit #{start},#{count}")
public List<Category> listByPage(@Param("start") int start, @Param("count")int count);
}
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.mapper.CategoryMapper;
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();
CategoryMapper mapper = session.getMapper(CategoryMapper.class);
List<Category> cs =mapper.listByPage(0, 5);
for (Category c : cs) {
System.out.println(c);
}
session.commit();
session.close();
}
}更多内容，点击理解： https://how2j.cn/k/mybatis/mybatis-annotation-pagination/1100.html
发表回复