标签：mybatis   basic   faq   mapper   parameter   

Mybatis基础: #{...} 和 ${...} 的区别

Map<String, Object> parms = new HashMap<String, Object>();
parms.put("table", "foo"); // 表名
parms.put("criteria", 37); // 查询过滤条件
List<Object> rows = mapper.generalSelect(parms);

<select id="generalSelect" parameterType="map">
  select * from ${table} where col1 = #{criteria}
</select>

select * from foo where col1 = ?

要使用LIKE语句该怎么写?

有两种使用LIKE的方法。(推荐使用)第一种方法是,在Java代码中添加SQL通配符。

String wildcardName = "%Smi%";
List<Name> names = mapper.selectLike(wildcardName);

<select id="selectLike">
  select * from foo where bar like #{value}
</select>

String wildcardName = "Smi";
List<Name> names = mapper.selectLike(wildcardName);

<select id="selectLike">
  select * from foo where bar like ‘%‘ || ‘${value}‘ || ‘%‘
</select>

如何执行批量插入?

<insert id="insertName">
  insert into names (name) values (#{value})
</insert>

List<String> names = new ArrayList<String>();
names.add("Fred");
names.add("Barney");
names.add("Betty");
names.add("Wilma");

// 注意这里 ExecutorType.BATCH
SqlSession sqlSession = sqlSessionFactory.openSession(ExecutorType.BATCH);
try {
  NameMapper mapper = sqlSession.getMapper(NameMapper.class);
  for (String name : names) {
    mapper.insertName(name);
  }
  sqlSession.commit();
} finally {
  sqlSession.close();
}

如何获取自动生成的(主)键值?

<insert id="insertName" useGeneratedKeys="true" keyProperty="id">
  insert into names (name) values (#{name})
</insert>

Name name = new Name();
name.setName("Fred");

int rows = mapper.insertName(name);
// 完成后,id已经被设置到对象中
System.out.println("rows inserted = " + rows);
System.out.println("generated key value = " + name.getId());

在mapper中如何传递多个参数?

import org.apache.ibatis.annotations.Param;
public interface UserMapper {
   User selectUser(@Param("username") String username, 
                   @Param("hashedPassword") String hashedPassword);
}

<select id=”selectUser” resultType=”User”>
  select id, username, hashedPassword
  from some_table
  where username = #{username}
  and hashedPassword = #{hashedPassword}
</select>

Mybatis基础: 常见问题与FAQ

标签：mybatis   basic   faq   mapper   parameter   

原文地址：http://blog.csdn.net/renfufei/article/details/39649707