主要记录Mybatis是如何映射传递的参数的。分四种来记录:1、java基本类型的传递、2、Java对象形式传递 3、多参数传递4、集合类型参数传递
以整形为例、映射文件:
<select id="getAuthorById" parameterType="int" resultType="org.alien.mybatis.samples.model.Author"> SELECT * FROM author WHERE id = #{id} </select>
映射方法:
Author getAuthorById(int id);
测试代码:
private AuthorMapper authorMapper; public AuthorMapperTest() { authorMapper = MybatisUtil.getSqlSession().getMapper(AuthorMapper.class); } @Test public void testGetAuthorById() throws Exception { Author author = authorMapper.getAuthorById(1); Assert.assertNotNull(author); }
以Author类为例、映射文件:
<select id="getAuthorWithValidate" parameterType="org.alien.mybatis.samples.model.Author" resultType="org.alien.mybatis.samples.model.Author"> SELECT * FROM author WHERE username = #{username} AND password = #{password} </select>
映射方法:
Author getAuthorWithValidate(Author author);
测试方法:
@Test public void testGetAuthorWithValidate() throws Exception { Author author = authorMapper.getAuthorWithValidate(new Author("star_year", "alien")); Assert.assertNotNull(author); }
多参数分为两种:1、将参数放在Map中。 2、使用Mybatis的注解@Param来指定。
Map类型映射文件:
<select id="getAuthorByMultiCondition" parameterType="hashMap" resultType="author"> SELECT * FROM ( SELECT A.*, ROWNUM RN FROM (SELECT * FROM author WHERE username LIKE '%' || #{username} || '%') A WHERE ROWNUM <= #{endRecord} ) WHERE RN >= #{startRecord} </select>
Map类型映射方法:
List<Author> getAuthorByMultiCondition(Map<String, Object> map);
Map类型测试方法:
@Test public void testGetAuthorByMultiCondition() throws Exception { Map<String, Object> map = new HashMap<>(); map.put("startRecord", 0); map.put("endRecord", 10); map.put("username", "star_year"); List<Author> authors = authorMapper.getAuthorByMultiCondition(map); Assert.assertNotNull(authors); }
@Param类型映射文件:
<select id="getAuthorByUsername" resultType="Author"> SELECT * FROM author WHERE username LIKE '%' || #{username} || '%' AND email LIKE '%' || #{email} || '%' </select>
@Param类型映射方法:
List<Author> getAuthorByUsername(@Param("username") String username, @Param("email") String email);
@Param类型测试方法:
@Test public void testGetAuthorByUsername() throws Exception { List<Author> authorList = authorMapper.getAuthorByUsername("star_year", "46185"); Assert.assertNotNull(authorList); }
常用与根据一系列id来做一些操作。
以Author类为例、映射文件:
<select id="getAuthorByIdCollection" resultType="author"> select * from author where id in <foreach collection="list" item="item" open="(" separator="," close=")"> #{item} </foreach> </select>
映射方法:
List<Author> getAuthorByIdCollection(List<Integer> idList);
测试方法:
@Test public void testGetAuthorByIdCollection() throws Exception { List<Integer> idList = new ArrayList<>(); idList.add(1); idList.add(2); List<Author> authorList = authorMapper.getAuthorByIdCollection(idList); Assert.assertNotNull(authorList); }
使用#{parameterName}引用参数的时候,Mybatis会把这个参数认为是一个字符串,例如传入参数是“Smith”,那么在SQL(Select * from emp where name = #{employeeName})使用的时候就会转换为Select * from emp where name = 'Smith';同时在SQL(Select * from emp where name = ${employeeName})使用的时候就会转换为Select * from emp where name = Smith。
再次,从安全性上考虑,能使用#尽量使用#来传参,因为这样可以有效防止SQL注入的问题。
更多内容:Mybatis 目录
github地址:https://github.com/andyChenHuaYing/scattered-items/tree/master/items-mybatis
源码下载地址:http://download.csdn.net/detail/chenghuaying/8713311
Author 类:
public class Author { private int id; private String username; private String password; private String email; private String bio; private String favouriteSection; //getter setter ... }