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SpringBoot系列教材 (十七)- CRUD+分页 - Springboot使用Mybatis实现完整的 增删改查 CRUD和分页

2020-04-22 03:26 633 查看

 

步骤1:Mybatis CRUD和分页
步骤2:先运行,看到效果,再学习
步骤3:模仿和排错
步骤4:基于前面的知识点
步骤5:pom.xml
步骤6:PageHelperConfig
步骤7:CategoryMapper
步骤8:CategoryController
步骤9:listCategory.jsp
步骤10:editCategory.jsp
步骤11:重启测试访问

步骤 1 : Mybatis CRUD和分页

这里使用Mybatis来做一个完整的CRUD和分页。 其中分页使用Mybatis 里讲解的PageHelper插件

步骤 2 : 先运行,看到效果,再学习

老规矩,先下载下载区(点击进入)的可运行项目,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效果。 
测试地址:

http:
//127.0.0.1:8080/listCategory


注: 启动方式是Springboot特有的,直接运行类:com.how2java.springboot.Application 的主方法。

步骤 3 : 模仿和排错

在确保可运行项目能够正确无误地运行之后,再严格照着教程的步骤,对代码模仿一遍。 
模仿过程难免代码有出入,导致无法得到期望的运行结果,此时此刻通过比较正确答案 ( 可运行项目 ) 和自己的代码,来定位问题所在。 
采用这种方式,学习有效果,排错有效率,可以较为明显地提升学习速度,跨过学习路上的各个槛。 

推荐使用diffmerge软件,进行文件夹比较。把你自己做的项目文件夹,和我的可运行项目文件夹进行比较。 
这个软件很牛逼的,可以知道文件夹里哪两个文件不对,并且很明显地标记出来 
这里提供了绿色安装和使用教程:diffmerge 下载和使用教程

步骤 4 : 基于前面的知识点

本知识点基于Springboot 中 Mybatis 的基本用法 进行扩展学习

步骤 5 : pom.xml

增加对PageHelper的支持

<dependency>

    
<groupId>com.github.pagehelper</groupId>

    
<artifactId>pagehelper</artifactId>

    
<version>
4.1
.
6
</version>

</dependency>

<?
xml
 
version
=
"1.0"
 
encoding
=
"UTF-8"
?>

<
project
 
xmlns
=
"http://maven.apache.org/POM/4.0.0"
 
xmlns:xsi
=
"http://www.w3.org/2001/XMLSchema-instance"

    
xsi:schemaLocation
=
"http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
>

    
<
modelVersion
>4.0.0</
modelVersion
>

 

  
<
groupId
>com.how2java</
groupId
>

  
<
artifactId
>springboot</
artifactId
>

  
<
version
>0.0.1-SNAPSHOT</
version
>

  
<
name
>springboot</
name
>

  
<
description
>springboot</
description
>

  
<
packaging
>war</
packaging
>

  
 

    
<
parent
>

        
<
groupId
>org.springframework.boot</
groupId
>

        
<
artifactId
>spring-boot-starter-parent</
artifactId
>

        
<
version
>1.5.9.RELEASE</
version
>

    
</
parent
>

 

    
<
dependencies
>

        
<
dependency
>

            
<
groupId
>org.springframework.boot</
groupId
>

            
<
artifactId
>spring-boot-starter-web</
artifactId
>

        
</
dependency
>

        
<
dependency
>

            
<
groupId
>org.springframework.boot</
groupId
>

            
<
artifactId
>spring-boot-starter-tomcat</
artifactId
>

            
 

        
</
dependency
>

        
<
dependency
>

              
<
groupId
>junit</
groupId
>

              
<
artifactId
>junit</
artifactId
>

              
<
version
>3.8.1</
version
>

              
<
scope
>test</
scope
>

        
</
dependency
>

        
<!-- servlet依赖. -->

        
<
dependency
>

              
<
groupId
>javax.servlet</
groupId
>

              
<
artifactId
>javax.servlet-api</
artifactId
>

              
 

        
</
dependency
>

              
<
dependency
>

                     
<
groupId
>javax.servlet</
groupId
>

                     
<
artifactId
>jstl</
artifactId
>

              
</
dependency
>

        
<!-- tomcat的支持.-->

        
<
dependency
>

               
<
groupId
>org.apache.tomcat.embed</
groupId
>

               
<
artifactId
>tomcat-embed-jasper</
artifactId
>

               
 

        
</
dependency
>     

        
<
dependency
>

            
<
groupId
>org.springframework.boot</
groupId
>

            
<
artifactId
>spring-boot-devtools</
artifactId
>

            
<
optional
>true</
optional
<!-- 这个需要为 true 热部署才有效 -->

        
</
dependency
>

        
 

        
<!-- mybatis -->

        
<
dependency
>

            
<
groupId
>org.mybatis.spring.boot</
groupId
>

            
<
artifactId
>mybatis-spring-boot-starter</
artifactId
>

            
<
version
>1.1.1</
version
>

        
</
dependency
>

 

        
<!-- mysql -->

        
<
dependency
>

            
<
groupId
>mysql</
groupId
>

            
<
artifactId
>mysql-connector-java</
artifactId
>

            
<
version
>5.1.21</
version
>

        
</
dependency
>

        
 

        
<!-- pagehelper -->

        
<
dependency
>

            
<
groupId
>com.github.pagehelper</
groupId
>

            
<
artifactId
>pagehelper</
artifactId
>

            
<
version
>4.1.6</
version
>

        
</
dependency
>

    
</
dependencies
>

 

    
<
properties
>

        
<
java.version
>1.8</
java.version
>

    
</
properties
>

 

    
<
build
>

        
<
plugins
>

            
<
plugin
>

                
<
groupId
>org.springframework.boot</
groupId
>

                
<
artifactId
>spring-boot-maven-plugin</
artifactId
>

            
</
plugin
>

        
</
plugins
>

    
</
build
>

 

</
project
>

步骤 6 : PageHelperConfig

注解@Configuration 表示PageHelperConfig 这个类是用来做配置的。
注解@Bean 表示启动PageHelper这个拦截器。

新增加一个包 com.how2java.springboot.config, 然后添加一个类PageHelperConfig ,其中进行PageHelper相关配置。
offsetAsPageNum:设置为true时,会将RowBounds第一个参数offset当成pageNum页码使用.

p.setProperty(
"offsetAsPageNum"
"true"
);


rowBoundsWithCount:设置为true时,使用RowBounds分页会进行count查询.

p.setProperty(
"rowBoundsWithCount"
"true"
);


reasonable:启用合理化时,如果pageNum<1会查询第一页,如果pageNum>pages会查询最后一页。

p.setProperty(
"reasonable"
"true"
);


注:RowBounds是什么鬼?我也没搞太清楚。。。反正这么复制粘贴就对了 :|

package
 
com.how2java.springboot.config;

 

import
 
java.util.Properties;

 

import
 
org.springframework.context.annotation.Bean;

import
 
org.springframework.context.annotation.Configuration;

 

import
 
com.github.pagehelper.PageHelper;

 

@Configuration

public
 
class
 
PageHelperConfig {

 

    
@Bean

    
public
 
PageHelper pageHelper() {

        
PageHelper pageHelper = 
new
 
PageHelper();

        
Properties p = 
new
 
Properties();

        
p.setProperty(
"offsetAsPageNum"
"true"
);

        
p.setProperty(
"rowBoundsWithCount"
"true"
);

        
p.setProperty(
"reasonable"
"true"
);

        
pageHelper.setProperties(p);

        
return
 
pageHelper;

    
}

}

步骤 7 : CategoryMapper

修改CategoryMapper,增加CRUD方法的支持。 其实就是调用不同的SQL语句。

package
 
com.how2java.springboot.mapper;

 

import
 
java.util.List;

 

import
 
org.apache.ibatis.annotations.Delete;

import
 
org.apache.ibatis.annotations.Insert;

import
 
org.apache.ibatis.annotations.Mapper;

import
 
org.apache.ibatis.annotations.Select;

import
 
org.apache.ibatis.annotations.Update;

 

import
 
com.how2java.springboot.pojo.Category;

 

@Mapper

public
 
interface
 
CategoryMapper {

 

    
@Select
(
"select * from category_ "
)

    
List<Category> findAll();

    
 

    
@Insert
(
" insert into category_ ( name ) values (#{name}) "

    
public
 
int
 
save(Category category);  

    
 

    
@Delete
(
" delete from category_ where id= #{id} "

    
public
 
void
 
delete(
int
 
id); 

        
 

    
@Select
(
"select * from category_ where id= #{id} "

    
public
 
Category get(
int
 
id); 

      
 

    
@Update
(
"update category_ set name=#{name} where id=#{id} "

    
public
 
int
 
update(Category category);  

 

}

步骤 8 : CategoryController

为CategoryController添加: 增加、删除、获取、修改映射

@RequestMapping
(
"/addCategory"
)

public
 
String listCategory(Category c) 
throws
 
Exception {

    
categoryMapper.save(c);

    
return
 
"redirect:listCategory"
;

}

@RequestMapping
(
"/deleteCategory"
)

public
 
String deleteCategory(Category c) 
throws
 
Exception {

    
categoryMapper.delete(c.getId());

    
return
 
"redirect:listCategory"
;

}

@RequestMapping
(
"/updateCategory"
)

public
 
String updateCategory(Category c) 
throws
 
Exception {

    
categoryMapper.update(c);

    
return
 
"redirect:listCategory"
;

}

@RequestMapping
(
"/editCategory"
)

public
 
String listCategory(
int
 
id,Model m) 
throws
 
Exception {

    
Category c= categoryMapper.get(id);

    
m.addAttribute(
"c"
, c);

    
return
 
"editCategory"
;

}



修改查询映射

@RequestMapping
(
"/listCategory"
)

public
 
String listCategory(Model m,
@RequestParam
(value = 
"start"
, defaultValue = 
"0"
int
start,
@RequestParam
(value = 
"size"
, defaultValue = 
"5"
int
 
size) 
throws
 
Exception {

    
PageHelper.startPage(start,size,
"id desc"
);

    
List<Category> cs=categoryMapper.findAll();

    
PageInfo<Category> page = 
new
 
PageInfo<>(cs);

    
m.addAttribute(
"page"
, page);         

    
return
 
"listCategory"
;

}


1. 在参数里接受当前是第几页 start ,以及每页显示多少条数据 size。 默认值分别是0和5。

@RequestParam
(value = 
"start"
, defaultValue = 
"0"
int
 
start,
@RequestParam
(value = 
"size"
, defaultValue = 
"5"


2. 根据start,size进行分页,并且设置id 倒排序

PageHelper.startPage(start,size,
"id desc"
);


3. 因为PageHelper的作用,这里就会返回当前分页的集合了

List<Category> cs=categoryMapper.findAll();


4. 根据返回的集合,创建PageInfo对象

PageInfo<Category> page = 
new
 
PageInfo<>(cs);


5. 把PageInfo对象扔进model,以供后续显示

m.addAttribute(
"page"
, page);      


6. 跳转到listCategory.jsp

return
 
"listCategory"
;

package
 
com.how2java.springboot.web;

import
 
java.util.List;

 

import
 
org.springframework.beans.factory.annotation.Autowired;

import
 
org.springframework.stereotype.Controller;

import
 
org.springframework.ui.Model;

import
 
org.springframework.web.bind.annotation.RequestMapping;

import
 
org.springframework.web.bind.annotation.RequestParam;

 

import
 
com.github.pagehelper.PageHelper;

import
 
com.github.pagehelper.PageInfo;

import
 
com.how2java.springboot.mapper.CategoryMapper;

import
 
com.how2java.springboot.pojo.Category;

  
 

@Controller

public
 
class
 
CategoryController {

    
@Autowired
 
CategoryMapper categoryMapper;

     
 

    
@RequestMapping
(
"/addCategory"
)

    
public
 
String listCategory(Category c) 
throws
 
Exception {

        
categoryMapper.save(c);

        
return
 
"redirect:listCategory"
;

    
}

    
@RequestMapping
(
"/deleteCategory"
)

    
public
 
String deleteCategory(Category c) 
throws
 
Exception {

        
categoryMapper.delete(c.getId());

        
return
 
"redirect:listCategory"
;

    
}

    
@RequestMapping
(
"/updateCategory"
)

    
public
 
String updateCategory(Category c) 
throws
 
Exception {

        
categoryMapper.update(c);

        
return
 
"redirect:listCategory"
;

    
}

    
@RequestMapping
(
"/editCategory"
)

    
public
 
String listCategory(
int
 
id,Model m) 
throws
 
Exception {

        
Category c= categoryMapper.get(id);

        
m.addAttribute(
"c"
, c);

        
return
 
"editCategory"
;

    
}

    
 

    
@RequestMapping
(
"/listCategory"
)

    
public
 
String listCategory(Model m,
@RequestParam
(value = 
"start"
, defaultValue = 
"0"
int
start,
@RequestParam
(value = 
"size"
, defaultValue = 
"5"
int
 
size) 
throws
 
Exception {

        
PageHelper.startPage(start,size,
"id desc"
);

        
List<Category> cs=categoryMapper.findAll();

        
PageInfo<Category> page = 
new
 
PageInfo<>(cs);

        
m.addAttribute(
"page"
, page);         

        
return
 
"listCategory"
;

    
}

    
 

}

步骤 9 : listCategory.jsp

通过page.getList遍历当前页面的Category对象。
在分页的时候通过page.pageNum获取当前页面,page.pages获取总页面数。
注:page.getList会返回一个泛型是Category的集合。

<%@ page language="java" contentType="text/html; charset=UTF-8"

    
pageEncoding="UTF-8"%>

 
 

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

   
 

<
div
 
align
=
"center"
>

 
 

</
div
>

 
 

<
div
 
style
=
"width:500px;margin:20px auto;text-align: center"
>

    
<
table
 
align
=
'center'
 
border
=
'1'
 
cellspacing
=
'0'
>

        
<
tr
>

            
<
td
>id</
td
>

            
<
td
>name</
td
>

            
<
td
>编辑</
td
>

            
<
td
>删除</
td
>

        
</
tr
>

        
<
c:forEach
 
items
=
"${page.list}"
 
var
=
"c"
 
varStatus
=
"st"
>

            
<
tr
>

                
<
td
>${c.id}</
td
>

                
<
td
>${c.name}</
td
>

                
<
td
><
a
 
href
=
"editCategory?id=${c.id}"
>编辑</
a
></
td
>

                
<
td
><
a
 
href
=
"deleteCategory?id=${c.id}"
>删除</
a
></
td
>

            
</
tr
>

        
</
c:forEach
>

         
 

    
</
table
>

    
<
br
>

    
<
div
>

                
<
a
 
href
=
"?start=1"
>[首  页]</
a
>

            
<
a
 
href
=
"?start=${page.pageNum-1}"
>[上一页]</
a
>

            
<
a
 
href
=
"?start=${page.pageNum+1}"
>[下一页]</
a
>

            
<
a
 
href
=
"?start=${page.pages}"
>[末  页]</
a
>

    
</
div
>

    
<
br
>

    
<
form
 
action
=
"addCategory"
 
method
=
"post"
>

     
 

    
name: <
input
 
name
=
"name"
> <
br
>

    
<
button
 
type
=
"submit"
>提交</
button
>

     
 

    
</
form
>

</
div
>

步骤 10 : editCategory.jsp

修改分类的页面

<%@ page language="java" contentType="text/html; charset=UTF-8"

 
pageEncoding="UTF-8" isELIgnored="false"%>

 
 

<
div
 
style
=
"margin:0px auto; width:500px"
>

 
 

<
form
 
action
=
"updateCategory"
 
method
=
"post"
>

 
 

name: <
input
 
name
=
"name"
 
value
=
"${c.name}"
> <
br
>

 
 

<
input
 
name
=
"id"
 
type
=
"hidden"
 
value
=
"${c.id}"
>

<
button
 
type
=
"submit"
>提交</
button
>

 
 

</
form
>

</
div
>

步骤 11 : 重启测试访问

因为在pom中增加了新jar的依赖,所以要手动重启,重启后访问测试地址:

http:
//127.0.0.1:8080/listCategory?start=2

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