java - MyBatis 查询中的参数未被替换

Question

以下是我在 BrandMapper.xml 中的选择查询。

<select id="getBrand" parameterType="String" resultMap="brandResult">
    SELECT 
        B.bid as bid, 
        B.bname as bname, 
        B.avg_price as avg_price, 
        B.total_number as total_number, 
        P.pid as pid, 
        P.pname as pname, 
        P.bid as pbid, 
        P.bname as pbname, 
        P.specs as pspecs, 
        P.price as price 
    from Brands B left outer join Products P on P.bid = B.bid 
    where B.bname = #{bname, jdbcType=VARCHAR}
</select>

这是界面

public interface BrandMapper {
    BrandDAO getBrand(String bname);
}

这是服务类

@Service
public class BrandService {
@Autowired
private BrandMapper brandMapper;
public BrandDAO getBrand(String bname) {
    System.out.println("Inside DBService getBrand");
    return brandMapper.getBrand(bname);
}
}

我的问题是 BrandService 中的 getBrand 函数返回一个 null 值。如果我将 BrandMapper.xml 中的参数 #{bname} 替换为硬编码字符串，它会工作并返回正确的类。我在这里做错了什么？是否有任何日志或任何可用的地方我可以看到正在构建的实际查询？感谢您的帮助。

我设法使用 log4j 启​​用登录，这是正在执行的查询

SELECT B.bid as bid, B.bname as bname, B.avg_price as avg_price, B.total_number as total_number, P.pid as pid, P.pname as pname, P.bid as pbid, P.bname as pbname, P.specs as pspecs, P.price as price from Brands B left outer join Products P on P.bid = B.bid where B.bname = ?

参数没有被替换。我不知道我在这里做错了什么。

Answer 1

问号是 Prepared Statements 中的占位符，记录的查询非常好并且看起来符合预期。实际值应作为单独的参数随查询传递到您的数据库。