java学习记录

一、修改数据

1.当修改数据时，会先判断该属性是否存在或者是否为空串

 <update id="editStaffItem">
        update staff
        <set>
            <if test='name!=null and name!=""'>
                name=#{name},
            if>
            <if test="salary!=null">
                salary=#{salary},
            if>
        set>
        <where>
            id=#{id}
        where>
    update>

2.在Dao层声明该方法

 int editStaffItem(Staff staff);

3.在Controller类中，编写代码来接收http请求

@PutMapping("staffitem")
    public String editStaffItem(Staff staff) {
        dao.editStaffItem(staff);
        return "success";
    }

二、模糊查询

1.在Dao层声明方法

 List getStaff(String checktext);

将查询的结果放在一个List中

2.在Mapper文件中编写数据库操作

 
    <select id="getStaff" resultType="com.easy.bean.Staff">
        select * from staff
        
        <where>
            
            <if test="checktext !=null and checktext !=''">
                
                <bind value="'%'+checktext+'%'" name="liketext">bind>
                name like  #{liketext}
            if>
        where>
    select>

3.控制类

  @GetMapping("staff")
    public CommonResult getStraff(String checktext) {
        List list=dao.getStaff(checktext);
        return CommonResult.success(list);
    }

三、根据工资的等级来获取职员的信息

1.Dao层

 List getStaffBySalary(String salarytext);

2.Mapper文件

  <select id="getStaffBySalary" resultType="com.easy.bean.Staff">
        select * from staff
        <where>
            
            <choose>
                <when test='salarytext == "低"'>
                    salary <= 5000
                when>
                <when test='salarytext == "中"'>
                    salary >5000 and salary<=8000
                when>
                <otherwise>
                    salary>8000
                otherwise>
            choose>
        where>
    select>

resultType表示输出的对象类型

3.控制类

  @GetMapping("staff/salary")
    public CommonResult getStaffBySalary(String salarytext) {
        List list=dao.getStaffBySalary(salarytext);
        return CommonResult.success(list);
    }

四、一次添加多组数据

1.Dao

int addList(List list);

2.Mapper文件

<insert id="addList" >
        insert into staff(code,name,salary,username,userpass)
        values
        <foreach collection="list" item="it"  separator=",">
            (#{it.code},#{it.name},#{it.salary},#{it.username},#{it.userpass})
        foreach>
 
    insert>

3.控制类

@PostMapping("staff")
    public String addStaff(Staff staff) {
        staff=new Staff();
        staff.setCode("10001");
        staff.setName("李思思");
        staff.setSalary(new BigDecimal(2000));
        staff.setUsername("lisisi");
        staff.setUserpass("123123");
        List list=new ArrayList();
        list.add(staff);
 
        staff=new Staff();
        staff.setCode("10002");
        staff.setName("小甜甜");
        staff.setSalary(new BigDecimal(2000));
        staff.setUsername("牛夫人");
        staff.setUserpass("123123");
        list.add(staff);
 
 
//		dao.addStaff(staff);
        dao.addList(list);
        return "success";
    }

五、Dao中接收多个参数

如果Dao中接收两个以上的参数就要使用@Param注解给参数起名字

1.Dao

int edit(@Param("id") int id,@Param("staff") Staff staff);

2.Mapper

 <update id="edit">
        upadate staff code=#{staff.code},name=#{staff.name}set where id=#{id}
    update>

六、多张表的映射

查询Staff表时也会显示Department表的部门信息

1.在Staff类中添加Department类的属性

 private Department dep;
 
    public Department getDep() {
        return dep;
    }
 
    public void setDep(Department dep) {
        this.dep = dep;
    }

2.Dao

List getStaffAndDep();

3.Mapper

    
    <resultMap id="staffAndDep" type="com.easy.bean.Staff">
        <association  column="dep_id" select="getStaffDep" property="dep" >association>
    resultMap>
 
    <select id="getStaffDep" resultType="com.easy.bean.Department">
        select * from department where id=#{dep_id}
    select>
 
    <select id="getStaffAndDep" resultMap="staffAndDep" >
        select * from staff
    select>

resultMap来定制映射的方式

type定义返回的对象是Staff类，通过dep_id来查询，将查询的内容放在dep列中，查询方法是select中指向的getStaffDep。

一对一用association

七、示例

查询部门时能显示内部职员的信息，一对多

1.Department

package com.easy.bean;
 
import java.io.Serializable;
import java.util.List;
 
public class Department implements Serializable {
    private int id;
    private String code;
    private String name;
    private List staffList;
 
    public List getStaffList() {
        return staffList;
    }
 
    public void setStaffList(List staffList) {
        this.staffList = staffList;
    }
 
    public int getId() {
        return id;
    }
 
    public void setId(int id) {
        this.id = id;
    }
 
    public String getCode() {
        return code;
    }
 
    public void setCode(String code) {
        this.code = code;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
}

2.Dao

package com.easy.dao;
 
import com.easy.bean.Department;
import org.apache.ibatis.annotations.Mapper;
 
import java.util.List;
 
@Mapper
public interface IDepartmentDao {
    int addDepartment(Department department);
    int delDepartment(int id);
    int editDepartment(Department department);
    List getDep();
}

3.Mapper

"1.0" encoding="UTF-8"?>
mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.easy.dao.IDepartmentDao">
    <cache eviction="FIFO" flushInterval="60000" size="512" readOnly="true" />
    <insert id="addDepartment">
        insert into department(code,name)
            value(#{code},#{name})
    insert>
    <delete id="delDepartment">
        delete from department where id=#{id}
    delete>
    <update id="editDepartment">
        update department set name=#{name} where id=#{id}
    update>
    <resultMap id="departmentAndStaff" type="com.easy.bean.Department">
        <result column="id" property="id">result>
        <collection fetchType="lazy" property="staffList" column="id" select="getDepStaff">collection>
    resultMap>
    <select id="getDepStaff" resultType="com.easy.bean.Staff">
        select *from staff where dep_id=#{id}
    select>
    <select id="getDep" resultMap="departmentAndStaff">
        select * from department
    select>
mapper>

4.控制类

package com.easy.controller;
 
import com.easy.bean.Department;
import com.easy.common.CommonResult;
import com.easy.dao.IDepartmentDao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.web.bind.annotation.*;
 
import java.util.List;
 
@RestController
public class DepartmentController {
    @Autowired
    IDepartmentDao dao;
    @PostMapping("department")
    public String addDepartment(Department department){
        dao.addDepartment(department);
        return "添加成功";
    }
    @DeleteMapping("department/{id}")
    public String delDepartment(@PathVariable int id){
        dao.delDepartment(id);
        return "删除成功";
    }
    @PutMapping("department")
    public String editDepartment(Department department){
        dao.editDepartment(department);
        return "修改成功";
    }
    @GetMapping ("dep")
//    @Transactional
    public CommonResult getDep(){
        List list =dao.getDep();
//        System.out.println("---------");
//        list =dao.getDep();
        return CommonResult.success(list);
    }
}

八、缓存

运行一次，就会加载一次

1.可以通过在Mapper文件中添加

<cache eviction="FIFO" flushInterval="60000" size="512" readOnly="true"

然后将在映射方式中加上fetchType属性

 <collection fetchType="lazy" property="staffList" column="id" select="getDepStaff">collection>

只有在系统调用时才会加载

2.@Transactional

在需要缓存的方法上加上@Transactional注解，并在启动类上加上@EnableTransactionManagement