码迷，mamicode.com
首页 > 其他好文 > 详细

Mybatis（三）

时间：2017-05-22 20:30:57      阅读：166      评论：0      收藏：0      [点我收藏+]

标签：inpu   tty   nfa   sep   bsp   tostring   更新   null   stream   

1 Mybaits--动态SQL

  • 动态SQL是Mybatis强大特性之一。极大的简化我们拼装SQL的操作。
  • 动态SQL元素和使用JSTL或其他类似基于XML的文本处理器相似。
  • Mybatis采用功能强大的基于OGNL的表达式来简化操作。
    • if
    • choose(when ,otherwise)　
    • trim(where,set)
    • foreach

 

1.1 动态SQL之if

package cn.demo2;



/**
 * 描述：POJO
 */
public class Employee {
    private Integer id;
    private String lastName;
    private String gender;
    private String email;
    private Department department;

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;

    }

    @Override
    public String toString() {
        return "Employee{" +
                "email=‘" + email + ‘\‘‘ +
                ", gender=‘" + gender + ‘\‘‘ +
                ", lastName=‘" + lastName + ‘\‘‘ +
                ", id=" + id +
                ‘}‘;
    }
}
package cn.demo2;


import java.util.List;

public interface IEmployeeDAO {


    public List<Employee> getConditionIf(Employee employee);

}
<?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="cn.demo2.IEmployeeDAO">




    <select id="getConditionIf" resultType="cn.demo2.Employee" >
      SELECT id,last_name lastName,email,gender from employee
      WHERE
      <if test="id != null">
        id = #{id}
      </if>
      <if test="lastName != null and lastName != ‘‘">
          and last_name like #{lastName}
      </if>
      <if test="email != null and email.trim() != ‘‘">
          and email = #{email}
      </if>
       <if test="gender == ‘男‘ or gender == ‘女‘">
          and gender = #{gender}
       </if>
    </select>


</mapper>
package cn.test;


import cn.demo2.Employee;
import cn.demo2.IEmployeeDAO;
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 org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MybatisTest2 {


    /**
     * 测试查询
     * @throws IOException
     */
    @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        Employee employee = new Employee();
        employee.setId(5);
        List<Employee> employees = dao.getConditionIf(employee);
        System.out.print(employees);

        session.close();
    }
}

 

1.2 动态SQL之where

  • 如果上面的程序中的id没有传入，那么拼接的SQL会多出and。
    • 解决方案一：在where之后加上1=1。
    • 解决方案二：Mybatis推荐使用where标签来将所有的查询条件包括在内，Mybatis就会将where标签中多出的and或or删除自动删除。并且where标签只会去掉第一个多出的and或or等。
package cn.demo2;



/**
 * 描述：POJO
 */
public class Employee {
    private Integer id;
    private String lastName;
    private String gender;
    private String email;
    private Department department;

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;

    }

    @Override
    public String toString() {
        return "Employee{" +
                "email=‘" + email + ‘\‘‘ +
                ", gender=‘" + gender + ‘\‘‘ +
                ", lastName=‘" + lastName + ‘\‘‘ +
                ", id=" + id +
                ‘}‘;
    }
}
<?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="cn.demo2.IEmployeeDAO">




    <select id="getConditionIf" resultType="cn.demo2.Employee" >
      SELECT id,last_name lastName,email,gender from employee
      <where>

          <if test="id != null">
              id = #{id}
          </if>
          <if test="lastName != null and lastName != ‘‘">
              and last_name like #{lastName}
          </if>
          <if test="email != null and email.trim() != ‘‘">
              and email = #{email}
          </if>
          <if test="gender == ‘男‘ or gender == ‘女‘">
              and gender = #{gender}
          </if>

      </where>

    </select>


</mapper>
package cn.test;


import cn.demo2.Employee;
import cn.demo2.IEmployeeDAO;
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 org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MybatisTest2 {


    /**
     * 测试查询
     * @throws IOException
     */
    @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        Employee employee = new Employee();
        employee.setLastName("%呵%");
        List<Employee> employees = dao.getConditionIf(employee);
        System.out.print(employees);

        session.close();
    }
}

 

1.2 动态SQL之trim

package cn.demo2;



/**
 * 描述：POJO
 */
public class Employee {
    private Integer id;
    private String lastName;
    private String gender;
    private String email;
    private Department department;

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;

    }

    @Override
    public String toString() {
        return "Employee{" +
                "email=‘" + email + ‘\‘‘ +
                ", gender=‘" + gender + ‘\‘‘ +
                ", lastName=‘" + lastName + ‘\‘‘ +
                ", id=" + id +
                ‘}‘;
    }
}
package cn.demo2;


import java.util.List;

public interface IEmployeeDAO {


    public List<Employee> getConditionIf(Employee employee);

}
<?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="cn.demo2.IEmployeeDAO">




    <select id="getConditionIf" resultType="cn.demo2.Employee" >
      SELECT id,last_name lastName,email,gender from employee
      <!--
        where标签职能消除前面多余的and或者or之类的语句，而如果and或or在之后，那么where就无能为力了
        trim可以来解决这样的问题
            prefix表示在拼接的SQL之前加前缀
            prefixOverrides是将前面多余的and或or等消除
            suffix和prefix相反
            prefixOverrides和prefixOverrides相反
      -->
      <trim prefix="where" suffixOverrides="and">

          <if test="id != null">
              id = #{id} and
          </if>
          <if test="lastName != null and lastName != ‘‘">
            last_name like #{lastName} and
          </if>
          <if test="email != null and email.trim() != ‘‘">
             email = #{email} and
          </if>
          <if test="gender == ‘男‘ or gender == ‘女‘">
              and gender = #{gender}
          </if>

      </trim>

    </select>


</mapper>
package cn.test;


import cn.demo2.Employee;
import cn.demo2.IEmployeeDAO;
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 org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MybatisTest2 {


    /**
     * 测试查询
     * @throws IOException
     */
    @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        Employee employee = new Employee();
        employee.setLastName("%呵%");
        List<Employee> employees = dao.getConditionIf(employee);
        System.out.print(employees);

        session.close();
    }
}

 

1.3 动态SQL之分支查询（和Java中的switch--case相似）

package cn.demo2;



/**
 * 描述：POJO
 */
public class Employee {
    private Integer id;
    private String lastName;
    private String gender;
    private String email;
    private Department department;

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;

    }

    @Override
    public String toString() {
        return "Employee{" +
                "email=‘" + email + ‘\‘‘ +
                ", gender=‘" + gender + ‘\‘‘ +
                ", lastName=‘" + lastName + ‘\‘‘ +
                ", id=" + id +
                ‘}‘;
    }
}
package cn.demo2;


import java.util.List;

public interface IEmployeeDAO {


    public List<Employee> getConditionIf(Employee employee);

}
<?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="cn.demo2.IEmployeeDAO">




    <select id="getConditionIf" resultType="cn.demo2.Employee" >
      SELECT id,last_name lastName,email,gender from employee
      <where>
          <choose>
              <when test="id != null">
                  id = #{id}
              </when>
              <when test="lastName != null">
                  last_name like  #{lastName}
              </when>
              <when test="email != null">
                  email = #{email}
              </when>
              <otherwise>
                  gender = #{gender}
              </otherwise>
          </choose>
      </where>
    </select>


</mapper>
package cn.test;


import cn.demo2.Employee;
import cn.demo2.IEmployeeDAO;
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 org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MybatisTest2 {


    /**
     * 测试查询
     * @throws IOException
     */
    @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        Employee employee = new Employee();
        employee.setLastName("%呵%");
        List<Employee> employees = dao.getConditionIf(employee);
        System.out.print(employees);

        session.close();
    }
}

技术分享

 

1.4 动态SQL之更新

 public void updateEmployee(Employee employee);
    <update id="updateEmployee" >
        update employee
        <set>
            <if test="email != null">
                email = #{email},
            </if>
            <if test="lastName != null">
                last_name = #{lastName}
            </if>
            <if test="gender != null">
                gender = #{gender}
            </if>
        </set>
        where id = #{id}
    </update>
 @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        Employee employee = new Employee();
        employee.setId(5);
        employee.setLastName("哈哈");
        dao.updateEmployee(employee);
        session.commit();
        session.close();
    }

 

1.5 动态SQL--forEach

public List<Employee> getEmpsByConditionForEach(List<Integer> ids);
<select id="getEmpsByConditionForEach" resultType="cn.demo2.Employee" >
        select * from employee where id IN
        <foreach collection="list" item="item_id" separator="," open="(" close=")" >
            #{item_id}
        </foreach>
    </select>
 /**
     * 测试查询
     * @throws IOException
     */
    @Test
    public  void demo1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        IEmployeeDAO dao = session.getMapper(IEmployeeDAO.class);
        dao.getEmpsByConditionForEach(Arrays.asList(5,6,7));
        session.close();
    }

 

 

 

 

 

 

 

　　

　　

 

Mybatis（三）

标签：inpu   tty   nfa   sep   bsp   tostring   更新   null   stream   

原文地址：http://www.cnblogs.com/xuweiweiailixing/p/6891198.html
踩
(0)
赞
(0)
   
举报
评论 一句话评论（0）
登录后才能评论！
分享档案
更多>
2021年07月29日 (22)
2021年07月28日 (40)
2021年07月27日 (32)
2021年07月26日 (79)
2021年07月23日 (29)
2021年07月22日 (30)
2021年07月21日 (42)
2021年07月20日 (16)
2021年07月19日 (90)
2021年07月16日 (35)
周排行
mamicode.com排行更多图片
更多
友情链接
兰亭集智   国之画   百度统计   站长统计   阿里云   chrome插件   新版天听网
关于我们 - 联系我们 - 留言反馈
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码！