mybatis的批量update

方法有三种：1.通过java代码batch方式，xml文件只需一条update语句。java代码繁琐

2.xml使用foreach，“;”分割多条update语句，要求：jdbc的url需加上allowMultiQueries=true。速度慢

3.xml使用foreach进行代码拼接，用了case...when...then...end，oracle好像不支持这种写法，mysql和sqlserver是可以的

xml文件：

<mapper namespace="com.dao.EmployeeDao">
    <!--可以通过改变实体类的字段来验证映射-->
    <update id="updateFirstWay">
        update employee set employee_name = #{employeeName},
        employee_gender = #{employeeGender},
        employee_salary = #{employeeSalary},
        dept_id = #{deptId}
        where employee_id = #{employeeId}
    </update>
 
    <update id="updateSecondWay">
        <foreach collection="list" item="emp" separator=";">
            update employee set employee_name = #{emp.employeeName},
            employee_gender = #{emp.employeeGender},
            employee_salary = #{emp.employeeSalary},
            dept_id = #{emp.deptId}
            where employee_id = #{emp.employeeId}
        </foreach>
    </update>
 
    <update id="updateThirdWay">
        update employee set
        employee_name= case employee_id
        <foreach collection="list" item="emp">
            when #{emp.employeeId} then #{emp.employeeName}
        </foreach>
        end, employee_gender= case employee_id
        <foreach collection="list" item="emp">
            when #{emp.employeeId} then #{emp.employeeGender}
        </foreach>
        end, employee_salary= case employee_id
        <foreach collection="list" item="emp">
            when #{emp.employeeId} then #{emp.employeeSalary}
        </foreach>
        end,dept_id= case employee_id
        <foreach collection="list" item="emp">
            when #{emp.employeeId} then #{emp.deptId}
        </foreach>
        end
        where
        <foreach collection="list" item="emp" separator="or">
            employee_id = #{emp.employeeId}
        </foreach>
    </update>
</mapper>

　　实体类：

package com.entity;
 
import java.math.BigDecimal;
 
public class Employee {
 
    private Integer employeeId;
    private String employeeName;
    private int employeeGender;
    private BigDecimal employeeSalary;
    private Integer deptId;
 
    public Employee() {
    }
 
    public Employee(Integer employeeId, String employeeName, int employeeGender, BigDecimal employeeSalary, Integer deptId) {
        this.employeeId = employeeId;
        this.employeeName = employeeName;
        this.employeeGender = employeeGender;
        this.employeeSalary = employeeSalary;
        this.deptId = deptId;
    }
 
    @Override
    public String toString() {
        return "Employee{" +
                "employeeId=" + employeeId +
                ", employeeName='" + employeeName + '\'' +
                ", employeeGender=" + employeeGender +
                ", employeeSalary=" + employeeSalary +
                ", deptId='" + deptId + '\'' +
                '}';
    }
 
    public Integer getEmployeeId() {
        return employeeId;
    }
 
    public void setEmployeeId(Integer employeeId) {
        this.employeeId = employeeId;
    }
 
    public String getEmployeeName() {
        return employeeName;
    }
 
    public void setEmployeeName(String employeeName) {
        this.employeeName = employeeName;
    }
 
    public int getEmployeeGender() {
        return employeeGender;
    }
 
    public void setEmployeeGender(int employeeGender) {
        this.employeeGender = employeeGender;
    }
 
    public BigDecimal getEmployeeSalary() {
        return employeeSalary;
    }
 
    public void setEmployeeSalary(BigDecimal employeeSalary) {
        this.employeeSalary = employeeSalary;
    }
 
    public Integer getDeptId() {
        return deptId;
    }
 
    public void setDeptId(Integer deptId) {
        this.deptId = deptId;
    }
}

　　EmployeeDao.class:

void updateFirstWay(Employee employee);
    int updateSecondWay(List<Employee> employees);
    int updateThirdWay(List<Employee> employees);

　　test代码：

@Test
    public void testUpdateFirstWay() {
        List<Employee> employees = new ArrayList<>();
        employees.add(new Employee(10,"傲慢", 1, new BigDecimal(9999), 1));
        employees.add(new Employee(11,"色欲", 0, new BigDecimal(8888), 2));
        employees.add(new Employee(12,"怠惰", 1, new BigDecimal(7777), 3));
        employees.add(new Employee(13,"贪婪", 1, new BigDecimal(6666), 4));
        employees.add(new Employee(14,"愤怒", 1, new BigDecimal(5555), 5));
        SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtil.getSqlSessionFactory();
        SqlSession sqlSession = sqlSessionFactory.openSession(ExecutorType.BATCH);
        EmployeeDao mapper = sqlSession.getMapper(EmployeeDao.class);
        try {
            for (int i = 0; i < employees.size(); i ++) {
                mapper.updateFirstWay(employees.get(i));
                if (i % 2 == 0 || i == employees.size() - 1) {
                    sqlSession.commit();
                }
            }
        } catch (Exception e) {
            sqlSession.rollback();
        } finally {
            sqlSession.close();
        }
    }
 
    @Test
    public void testUpdateSecondWay() {
        List<Employee> employees = new ArrayList<>();
        employees.add(new Employee(15,"傲慢", 1, new BigDecimal(9999), 1));
        employees.add(new Employee(16,"色欲", 1, new BigDecimal(8888), 2));
        employees.add(new Employee(17,"怠惰", 1, new BigDecimal(7777), 3));
        employees.add(new Employee(18,"贪婪", 0, new BigDecimal(6666), 4));
        employees.add(new Employee(19,"愤怒", 1, new BigDecimal(5555), 5));
        EmployeeDao employeeDao = MapperFactory.generateMapper(EmployeeDao.class);
        employeeDao.updateSecondWay(employees);
    }
 
    @Test
    public void testUpdateThirdWay() {
        List<Employee> employees = new ArrayList<>();
        employees.add(new Employee(1,"傲慢", 1, new BigDecimal(9999), 1));
        employees.add(new Employee(2,"色欲", 1, new BigDecimal(8888), 2));
        EmployeeDao employeeDao = MapperFactory.generateMapper(EmployeeDao.class);
        employeeDao.updateThirdWay(employees);
    }

　　总结：#{}里面写的是实体类的字段，已经测试过了。

最后：根据实际要求，每个字段是要判断是否为空的，例

<update id="updateFirstWay">
        update employee set
        <if test="b != null and b != ''">
            employee_name = #{b},
        </if>
         <if test="c != null and c != ''">
             employee_gender = #{c},
         </if>
          <if test="d != null and d != ''">
              employee_salary = #{d},
          </if>
          <if test="e != null and e !=''">
              dept_id = #{e}
          </if>
        where employee_id = #{a}
    </update>

　　因为当只修改部分数据库的列的值，而不是全部列的时候，就需要将不要修改的字段跳过。上面的代码有漏洞，当所有列都不修改的时候会出错，修改代码的话以后再说，累了

有个bug:数据库的binary类型，实体类写的Integer，但是写在ongl里面判断x != null and x != ''，如果是0的话，那么这句话会跳过，false