Spring+MyBatis框架中sql语句的书写，数据集的传递以及多表关联查询

　　在很多Java EE项目中，Spring+MyBatis框架经常被用到，项目搭建在这里不再赘述，现在要将的是如何在项目中书写，增删改查的语句，如何操作数据库，以及后台如何获取数据，如何进行关联查询，以及MyBatis的分页问题。

　　首先先看看项目的架构，方便后边叙述。

　　　这个项目中是一个Sping+MyBatis的完整demo（这边将页面没有展示。）这次的主题主要是后台数据处理逻辑。接下来为大家逐一介绍各个文件，

　　org.config   Spring配置包括数据库的链接信息

　　org.controller　　逻辑控制，也就是MVC中的C

　　org.dao　　　　　　接口基类

　　org.entity 　　　　　实体以及MyBatis语句

　　org.util　　　　　　　工具类

　　在数据库中存在两张表，分别为Customer_info，order_info。用这两张表格最后实现多表格的关联查询。

　　第一步骤：建立与数据库表格字段相一致的实体类：

　　customerInfo.java

package org.entity;
//实现该接口--序列化，将对象写入文件
import java.io.Serializable;
import java.util.List;

public class CustomerInfo implements Serializable {
    private Integer customer_id;//客户信息的id
    private String  customer_name;//客户姓名
    private String identity_no;//身份证号码
    private String job_add;//工作单位
    private String tel;//座机号码
    private String cellphone;//移动电话
    private String adds;//联系地址
    private Integer post;//邮编
    private String mail;//电子邮箱
    //关联查询属性orderInfo
    private List<OrderInfo> orderInfos;

    public List<OrderInfo> getOrderInfos() {
        return orderInfos;
    }
    public void setOrderInfos(List<OrderInfo> orderInfos) {
        this.orderInfos = orderInfos;
    }

    public Integer getCustomer_id() {
        return customer_id;
    }
    public void setCustomer_id(Integer customer_id) {
        this.customer_id = customer_id;
    }
    public String getCustomer_name() {
        return customer_name;
    }
    public void setCustomer_name(String customer_name) {
        this.customer_name = customer_name;
    }
    public String getIdentity_no() {
        return identity_no;
    }
    public void setIdentity_no(String identity_no) {
        this.identity_no = identity_no;
    }
    public String getJob_add() {
        return job_add;
    }
    public void setJob_add(String job_add) {
        this.job_add = job_add;
    }
    public String getTel() {
        return tel;
    }
    public void setTel(String tel) {
        this.tel = tel;
    }
    public String getCellphone() {
        return cellphone;
    }
    public void setCellphone(String cellphone) {
        this.cellphone = cellphone;
    }
    public String getAdds() {
        return adds;
    }
    public void setAdds(String adds) {
        this.adds = adds;
    }
    public Integer getPost() {
        return post;
    }
    public void setPost(Integer post) {
        this.post = post;
    }
    public String getMail() {
        return mail;
    }
    public void setMail(String mail) {
        this.mail = mail;
    }

}

　　OrderInfo.java

 package org.entity;

 import java.io.Serializable;
 import java.sql.Date;

 //订单退货单
 public class OrderInfo implements Serializable{
     private Integer order_id;//订单（退货单）信息的id
     private String order_type;//订单类型
     private String order_status;//订单状态
     private Integer product_id;//商品id
     private Integer product_account;//商品数量
     private Double pay_money;//总额
     private Integer customer_id;//客户id
     private Date start_date;//开始日期
     private Date deadline;//要求完成日期
     private String return_reason;//退货原因
     public Integer getOrder_id() {
         return order_id;
     }
     public void setOrder_id(Integer order_id) {
         this.order_id = order_id;
     }

     public String getOrder_type() {
         return order_type;
     }
     public void setOrder_type(String order_type) {
         this.order_type = order_type;
     }
     public String getOrder_status() {
         return order_status;
     }
     public void setOrder_status(String order_status) {
         this.order_status = order_status;
     }
     public Integer getProduct_id() {
         return product_id;
     }
     public void setProduct_id(Integer product_id) {
         this.product_id = product_id;
     }
     public Integer getProduct_account() {
         return product_account;
     }
     public void setProduct_account(Integer product_account) {
         this.product_account = product_account;
     }
     public Double getPay_money() {
         return pay_money;
     }
     public void setPay_money(Double pay_money) {
         this.pay_money = pay_money;
     }
     public Integer getCustomer_id() {
         return customer_id;
     }
     public void setCustomer_id(Integer customer_id) {
         this.customer_id = customer_id;
     }
     public Date getStart_date() {
         return start_date;
     }
     public void setStart_date(Date start_date) {
         this.start_date = start_date;
     }
     public Date getDeadline() {
         return deadline;
     }
     public void setDeadline(Date deadline) {
         this.deadline = deadline;
     }
     public String getReturn_reason() {
         return return_reason;
     }
     public void setReturn_reason(String return_reason) {
         this.return_reason = return_reason;
     }

 }

　　Page.java

 package org.entity;

 public class Page {
     //显示第几页数据,默认第一页
     private Integer page=1;
     //一页显示几条,默认5条
     private Integer pageSize = 3;
     //最大页数
     private Integer totalPage=1;

     public Integer getTotalPage() {
         return totalPage;
     }
     public void setTotalPage(Integer totalPage) {
         this.totalPage = totalPage;
     }
     //利用page和pageSize计算begin起点
     public Integer getBegin(){
         return (page-1)*pageSize;
     }
     //利用page和pageSize计算end结束点
     public Integer getEnd(){
         return page*pageSize+1;
     }

     public Integer getPage() {
         return page;
     }
     public void setPage(Integer page) {
         this.page = page;
     }
     public Integer getPageSize() {
         return pageSize;
     }
     public void setPageSize(Integer pageSize) {
         this.pageSize = pageSize;
     }
 }

　　在接下来的这两个文件中，里边详细些了如何进行增删改查，以及多表之间的查询操作等。其中sql语句中的每一个id对应着dao方法中的方法名称。dao文件的内容如下;

　　customer.xml

 <?xml version="1.0" encoding="UTF-8" ?>
 <!DOCTYPE mapper PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN"
  "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">
 <mapper namespace="org.dao.CustomerInfoMapperDao">

     <select id="findAll"
     resultType="org.entity.CustomerInfo">
         select * from customer_info
     </select>
     <delete id="deleteCustomer" parameterType="int">
         delete from customer_info where customer_id=#{id}
     </delete>

     <insert id="saveCustomer" parameterType="org.entity.CustomerInfo">
         insert into Customer_info(customer_id,customer_name,identity_no,
         job_add,tel,cellphone,Adds,post,mail)
         values(customer_seq.nextval,#{customer_name,jdbcType=VARCHAR},#{identity_no,jdbcType=VARCHAR},
         #{job_add,jdbcType=VARCHAR},#{tel,jdbcType=VARCHAR},#{cellphone,jdbcType=VARCHAR},
         #{adds,jdbcType=VARCHAR},#{post,jdbcType=NUMERIC},#{mail,jdbcType=VARCHAR})
     </insert>

     <select id="findByCustomerName"
         parameterType="java.lang.String"
         resultType="org.entity.CustomerInfo">
         select * from customer_info where customer_name=#{customer_name}
     </select>
     <select id="findByCustomerId" parameterType="int" resultType="org.entity.CustomerInfo">
         select * from customer_info where customer_id=#{customer_id,jdbcType=NUMERIC}
     </select>

     <update id="updateCustomerInfo" parameterType="org.entity.CustomerInfo">
         update customer_info set customer_name=#{customer_name,jdbcType=VARCHAR},
         identity_no=#{identity_no,jdbcType=VARCHAR},
         job_add=#{job_add,jdbcType=VARCHAR},tel=#{tel,jdbcType=VARCHAR},
         cellphone=#{cellphone,jdbcType=VARCHAR},adds=#{adds,jdbcType=VARCHAR},
         post=#{post,jdbcType=NUMERIC},mail=#{mail,jdbcType=VARCHAR}
         where customer_id=#{customer_id,jdbcType=NUMERIC}
     </update>
     <select id="findPage" parameterType="org.entity.Page" resultType="org.entity.CustomerInfo" >
         select *
         FROM (select c1.*,rownum rn
         FROM (select * FROM customer_info order by customer_id)c1)
         where rn&gt;#{begin} and rn&lt;#{end}

     </select>

     <select id="findRows" resultType="int" >
         select count(*) from customer_info
     </select>

     <select id="somethingNotIn" resultType="返回所对应的实体">
             SELECT * FROM user  WHERE username NOT IN ('zhang','wang')
     </select>

     <select id="findByCuId" parameterType="java.lang.Integer" resultMap="cuAndOrderResult">
     select  o.customer_id,o.order_id,o.order_type,o.order_status,o.product_id,o.product_account,o.start_date,
     c.customer_name,c.cellphone,c.adds
     from order_info o left join customer_info c on(o.customer_id=c.customer_id)
     where o.customer_id=#{customer_id}
     </select>
     <resultMap id="cuAndOrderResult" type="org.entity.CustomerInfo" >
     <id property="customer_id" column="customer_id"/>
     <result property="customer_name" column="customer_name"/>
     <result property="cellphone" column="cellphone"/>
     <result property="adds" column="adds"/>
     <collection ofType="org.entity.OrderInfo"
             property="orderInfos"  column="customer_id" javaType="java.util.List">
     <id property="order_id" column="order_id"/>
     <result property="order_type" column="order_type"/>
     <result property="order_status" column="order_status"/>
     <result property="product_id" column="product_id"/>
     <result property="product_account" column="product_account"/>
     <result property="start_date" column="start_date"/>
     </collection>
     </resultMap>

          <!--
      <select id="findByCuId"
         parameterType="java.lang.Integer"
         resultMap="cuAndOrderResult">
              select  o.customer_id,o.order_id,o.order_type,o.order_status,o.product_id,o.product_account,
     c.customer_name,c.cellphone,c.adds
     from order_info o join customer_info c on(o.customer_id=c.customer_id)
     where o.customer_id=#{customer_id}
     select * from customer_info where customer_id=#{customer_id}

     </select>
     <select id="selectOrderInfo"
         parameterType="int"
         resultType="org.entity.OrderInfo">
         select * from order_info where customer_id=#{customer_id}
     </select>
     <resultMap id="cuAndOrderResult" type="org.entity.CustomerInfo">
         <id column="customer_id" property="customer_id" />
         <collection ofType="org.entity.OrderInfo"
             property="orderInfos" javaType="java.util.ArrayList"
             column="customer_id" select="selectOrderInfo">
         </collection>
     </resultMap>

       -->

 </mapper>

　　OrderInfo.xml

 <?xml version="1.0" encoding="UTF-8" ?>
 <!DOCTYPE mapper PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN"
  "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">
 <mapper namespace="org.dao.OrderInfoMapperDao">

     <select id="findAll"
     resultType="org.entity.OrderInfo">
         select * from Order_Info
     </select>

     <select id="findPage" parameterType="org.entity.Page" resultType="org.entity.OrderInfo" >
         select *
         FROM (select c1.*,rownum rn
         FROM (select * FROM Order_Info order by order_id)c1)
         where rn&gt;#{begin} and rn&lt;#{end}

     </select>

     <select id="findRows" resultType="int" >
         select count(*) from Order_Info
     </select>

 </mapper>

　　CustomerInfoMapperDao.java

 package org.dao;

 import java.util.List;

 import org.entity.CustomerInfo;
 import org.entity.Page;
 import org.util.MyBatisDao;

 //xml文件中的方法，然后在Controller中调用该方法
 @MyBatisDao
 public interface CustomerInfoMapperDao {
     public List<CustomerInfo> findAll();
     public void deleteCustomer(int id);
     public void saveCustomer(CustomerInfo customer);
     public CustomerInfo findByCustomerName(String customer_name);
     public CustomerInfo findByCustomerId(int id);
     public List<CustomerInfo> findByCuId(int id);//根据cuid查询客户的订单信息
     public void updateCustomerInfo(CustomerInfo customer);
     //分页操作
     public  List<CustomerInfo> findPage(Page page);
     public int findRows();

 }

　　接下来主要来说一下，MyBatis中的多表关联问题。多表关联主要对应customer.xml中的这段代码；

在controller中的代码如下：

从图中可以看到，在这边使用了一个增强的for循环来进行处理，这样就实现了多表之间的关联查询，接下来将数据显示到前台页面即可。

主要代码：

 List<CustomerInfo> list = dao.findByCuId(id);
         String ls = "";
         List<OrderInfo> cu = null;
         for(CustomerInfo cus:list){
             cu=cus.getOrderInfos();
         }
         model.addAttribute("customers", list);
         model2.addAttribute("order",cu);