MyBatis总结(二十八)--任务39：MyBatis_动态sql_if_判断&OGNL

本文内容来自尚硅谷

Junit

package com.atguigu.mybatis.test;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

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 com.atguigu.mybatis.bean.Department;
import com.atguigu.mybatis.bean.Employee;
import com.atguigu.mybatis.dao.DepartmentMapper;
import com.atguigu.mybatis.dao.EmployeeMapper;
import com.atguigu.mybatis.dao.EmployeeMapperAnnotation;
import com.atguigu.mybatis.dao.EmployeeMapperDynamicSQL;
import com.atguigu.mybatis.dao.EmployeeMapperPlus;

/**
 * 1、接口式编程
 * 	原生：		Dao		====>  DaoImpl
 * 	mybatis：	Mapper	====>  xxMapper.xml
 * 
 * 2、SqlSession代表和数据库的一次会话；用完必须关闭；
 * 3、SqlSession和connection一样她都是非线程安全。每次使用都应该去获取新的对象。
 * 4、mapper接口没有实现类，但是mybatis会为这个接口生成一个代理对象。
 * 		（将接口和xml进行绑定）
 * 		EmployeeMapper empMapper =	sqlSession.getMapper(EmployeeMapper.class);
 * 5、两个重要的配置文件：
 * 		mybatis的全局配置文件：包含数据库连接池信息，事务管理器信息等...系统运行环境信息
 * 		sql映射文件：保存了每一个sql语句的映射信息：
 * 					将sql抽取出来。	
 * 
 * 
 * @author lfy
 *
 */
public class MyBatisTest {
	

	public SqlSessionFactory getSqlSessionFactory() throws IOException {
		String resource = "mybatis-config.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		return new SqlSessionFactoryBuilder().build(inputStream);
	}
	
	@Test
	public void testDynamicSql() throws IOException{
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession openSession = sqlSessionFactory.openSession();
		try{
			EmployeeMapperDynamicSQL mapper = openSession.getMapper(EmployeeMapperDynamicSQL.class);
			Employee employee = new Employee(1, "%e%", null, null);
			List<Employee> emps = mapper.getEmpsByConditionIf(employee );
			for (Employee emp : emps) {
				System.out.println(emp);
			}
		}finally{
			openSession.close();
		}
	}

}

dao

package com.atguigu.mybatis.dao;

import java.util.List;

import org.apache.ibatis.annotations.Param;

import com.atguigu.mybatis.bean.Employee;

public interface EmployeeMapperDynamicSQL {
	
	public List<Employee> getEmpsTestInnerParameter(Employee employee);
	
	//携带了哪个字段查询条件就带上这个字段的值
	public List<Employee> getEmpsByConditionIf(Employee employee);
	
	public List<Employee> getEmpsByConditionTrim(Employee employee);
	
	public List<Employee> getEmpsByConditionChoose(Employee employee);
	
	public void updateEmp(Employee employee);
	
	//查询员工id'在给定集合中的
	public List<Employee> getEmpsByConditionForeach(@Param("ids")List<Integer> ids);
	
	public void addEmps(@Param("emps")List<Employee> emps);

}

xml

遇见特殊符号应该去写转义字符&&

	<!-- 
• if:判断
• choose (when, otherwise):分支选择；带了break的swtich-case
	如果带了id就用id查，如果带了lastName就用lastName查;只会进入其中一个
• trim 字符串截取(where(封装查询条件), set(封装修改条件))
• foreach 遍历集合
	 -->
	 <!-- 查询员工，要求，携带了哪个字段查询条件就带上这个字段的值 -->
	 <!-- public List<Employee> getEmpsByConditionIf(Employee employee); -->
	 <select id="getEmpsByConditionIf" resultType="com.atguigu.mybatis.bean.Employee">
	 	select * from tbl_employee
	 	<!-- where -->
	 	<where>
		 	<!-- test：判断表达式（OGNL）
		 	OGNL参照PPT或者官方文档。
		 	  	 c:if  test
		 	从参数中取值进行判断
		 	
		 	遇见特殊符号应该去写转义字符：
		 	&&：
		 	-->
		 	<if test="id!=null">
		 		id=#{id}
		 	</if>
		 	<if test="lastName!=null &amp;&amp; lastName!=&quot;&quot;">
		 		and last_name like #{lastName}
		 	</if>
		 	<if test="email!=null and email.trim()!=&quot;&quot;">
		 		and email=#{email}
		 	</if> 
		 	<!-- ognl会进行字符串与数字的转换判断  "0"==0 -->
		 	<if test="gender==0 or gender==1">
		 	 	and gender=#{gender}
		 	</if>
	 	</where>
	 </select>

javabean

package com.atguigu.mybatis.bean;

import org.apache.ibatis.type.Alias;

@Alias("emp")
public class Employee {
	
	private Integer id;
	private String lastName;
	private String email;
	private String gender;
	private Department dept;
	
	public Employee() {
		super();
	}
	
	
	
	public Employee(Integer id, String lastName, String email, String gender,
			Department dept) {
		super();
		this.id = id;
		this.lastName = lastName;
		this.email = email;
		this.gender = gender;
		this.dept = dept;
	}



	public Employee(Integer id, String lastName, String email, String gender) {
		super();
		this.id = id;
		this.lastName = lastName;
		this.email = email;
		this.gender = gender;
	}
	
	
	

	public Department getDept() {
		return dept;
	}

	public void setDept(Department dept) {
		this.dept = dept;
	}

	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getLastName() {
		return lastName;
	}
	public void setLastName(String lastName) {
		this.lastName = lastName;
	}
	public String getEmail() {
		return email;
	}
	public void setEmail(String email) {
		this.email = email;
	}
	public String getGender() {
		return gender;
	}
	public void setGender(String gender) {
		this.gender = gender;
	}
	@Override
	public String toString() {
		return "Employee [id=" + id + ", lastName=" + lastName + ", email="
				+ email + ", gender=" + gender + "]";
	}
	
	

}