使用 if where foreach标签对映射配置文件中sql语句进行动态配置
1、首先在dao接口中设置两个查询方法
1 package sun.dao; 2 3 import sun.domain.QueryObj; 4 import sun.domain.User; 5 6 import java.util.List; 7 8 public interface UserDao { 9 10 /** 11 * 根据已有条件进行查询(if where) 12 */ 13 List<User> findUserByCondition(User user); 14 15 /** 16 * 根据集合中的id进行查询(if where foreach) 17 */ 18 List<User> findUserByList(QueryObj qobj); 19 }
2、配置映射配置文件(使用if where foreach三种标签)
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE mapper 3 PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 4 "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> 5 6 <mapper namespace="sun.dao.UserDao"> 7 <resultMap id="userMap" type="sun.domain.User"> 8 <!--主键字段对应--> 9 <id property="user_id" column="id"></id> 10 <!--非主键关系对应--> 11 <result property="user_name" column="username"></result> 12 <result property="user_birthday" column="birthday"></result> 13 <result property="user_address" column="address"></result> 14 <result property="user_sex" column="sex"></result> 15 </resultMap> 16 17 <!--公共sql语句抽取--> 18 <sql id="defaultSelect"> 19 select * from user 20 </sql> 21 22 <!--根据条件进行查询--> 23 <select id="findUserByCondition" resultMap="userMap" parameterType="user"> 24 <include refid="defaultSelect"></include> 25 <where> 26 <if test="user_name!=null"> 27 and username=#{user_name} 28 </if> 29 <if test="user_sex!=null"> 30 and sex=#{user_sex} 31 </if> 32 </where> 33 </select> 34 <!--根据id列表进行查询--> 35 <select id="findUserByList" parameterType="queryobj" resultMap="userMap"> 36 <include refid="defaultSelect"></include> 37 <where> 38 <if test="ids!=null and ids.size()>0"> 39 <foreach collection="ids" open="id in (" close=")" item="id" separator=","> 40 #{id} 41 </foreach> 42 </if> 43 </where> 44 </select> 45 </mapper>
在映射配置文件中可以使用sql标签对常用的sql语句进行抽取,在操作标签内如果需要使用该sql语句可使用include标签进行导入即可。
(注意:使用sql语句进行抽取时,sql语句后面不要添加分号,否则会导致在操作标签内引用后拼接sql字符串时造成错误)
如果在该段代码中有关于parameterType未使用全限定类名的疑惑请参考Mybatis项目构建和CURD操作博客最下面的properties标签和typeAliases标签的使用
3、测试类中进行测试
1 package sun.test; 2 3 4 import org.apache.ibatis.io.Resources; 5 import org.apache.ibatis.session.SqlSession; 6 import org.apache.ibatis.session.SqlSessionFactory; 7 import org.apache.ibatis.session.SqlSessionFactoryBuilder; 8 import org.junit.After; 9 import org.junit.Before; 10 import org.junit.Test; 11 import sun.dao.UserDao; 12 import sun.domain.QueryObj; 13 import sun.domain.User; 14 15 import java.io.IOException; 16 import java.io.InputStream; 17 import java.util.ArrayList; 18 import java.util.Date; 19 import java.util.List; 20 21 public class MybatisTest { 22 23 private InputStream in; 24 private SqlSession sqlSession; 25 private UserDao userDao; 26 27 @Before 28 public void init() throws IOException { 29 // 读取配置文件 30 in = Resources.getResourceAsStream("SqlMapConfig.xml"); 31 // 创建SqlSessionFactory 32 SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder(); 33 SqlSessionFactory factory = builder.build(in); 34 // 使用工厂生产sqlsession对象 35 sqlSession = factory.openSession(); 36 // 使用sqlsession创建UserDao接口代理对象 37 userDao = sqlSession.getMapper(UserDao.class); 38 } 39 40 @After 41 public void destory() throws IOException { 42 sqlSession.commit(); 43 sqlSession.close(); 44 in.close(); 45 } 46 47 48 @Test 49 public void conditionTest(){ 50 User user = new User(); 51 user.setUser_name("kelvin"); 52 user.setUser_sex("女"); 53 List<User> users = userDao.findUserByCondition(user); 54 for (User user1 : users) { 55 System.out.println(user1); 56 } 57 } 58 59 @Test 60 public void ids(){ 61 QueryObj queryObj = new QueryObj(); 62 ArrayList<Integer> ids = new ArrayList<Integer>(); 63 ids.add(51); 64 ids.add(52); 65 ids.add(53); 66 queryObj.setIds(ids); 67 List<User> users = userDao.findUserByList(queryObj); 68 for (User user : users) { 69 System.out.println(user); 70 } 71 72 } 73 }
测试结果如下: