SSM+VUE前后端分离项目，后端mapper.xml里的SQL语句在执行时遇到的问题
¥15
xml
sql
spring
后端现在有两个Mapper.xml文件，一个UserMapper，一个TokenMapper.在UserServiceImpl.java文件里执行
User user = userMapper.selectByExample(userExample);
```java
List<Token> theToken = tokenMapper.selectTokenByExample(tokenExample);
```的时候，查询到记录后直接就不往下继续跑了，后面的代码根本不执行。以下是一些相关代码：
```java
@Service
public class TokenServiceImpl implements TokenService {
@Autowired
private TokenMapper tokenMapper;
@Override
public Token findToken(String token) {
TokenExample tokenExample = new TokenExample();
TokenExample.Criteria criteria = tokenExample.createCriteria();
criteria.andTokenEqualTo(token);
List<Token> theToken = tokenMapper.selectTokenByExample(tokenExample);
System.out.println("tokenList:"+theToken);
return theToken.get(0);
}
@Override
public void addToken(Token token) {
tokenMapper.insert(token);
}
@Override
public void updateToken(Token token) {
tokenMapper.updateByPrimaryKeySelective(token);
}
}
<resultMap id="BaseResultMap" type="com.ssm.entity.Token">
<id column="id" property="id" />
<result column="user_id" property="userId" />
<result column="token" property="token" />
<result column="applyTime" property="applyTime" />
<result column="expireTime" property="expireTime" />
<result column="countAuth" property="countAuth" />
<result column="maxCountAuth" property="maxCountAuth" />
<result column="ussAge" property="ussAge" />
</resultMap>
<sql id="Example_Where_Clause">
<where>
<foreach collection="oredCriteria" item="criteria" separator="or">
<if test="criteria.valid">
<trim prefix="(" prefixOverrides="and" suffix=")">
<foreach collection="criteria.criteria" item="criterion">
<choose>
<when test="criterion.noValue">
and ${criterion.condition}
</when>
<when test="criterion.singleValue">
and ${criterion.condition} #{criterion.value}
</when>
<when test="criterion.betweenValue">
and ${criterion.condition} #{criterion.value} and #{criterion.secondValue}
</when>
<when test="criterion.listValue">
and ${criterion.condition}
<foreach close=")" collection="criterion.value" item="listItem" open="(" separator=",">
#{listItem}
</foreach>
</when>
</choose>
</foreach>
</trim>
</if>
</foreach>
</where>
</sql>
<sql id="Base_Column_List">
id, userId, token, applyTime, expireTime, countAuth, maxCountAuth, ussAge
</sql>
<select id="selectTokenByExample" parameterType="com.ssm.entity.TokenExample" resultMap="BaseResultMap">
select
<if test="distinct">
distinct
</if>
'true' as QUERYID,
<include refid="Base_Column_List" />
from tokens
<if test="_parameter != null">
<include refid="Example_Where_Clause" />
</if>
<if test="orderByClause != null">
order by ${orderByClause}
</if>
</select>
UserMapper.xml里的代码和TokenMapper.xml差不多，就是resultMap和Base_Column_List是各自实体类还有数据表的内容。
然后下面是执行Mapper.xml里的SQL的时候输出的日志：
UserMapper里的SQL执行日志
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@367b1aaa] was not registered for synchronization because synchronization is not active
JDBC Connection [jdbc:mysql://localhost:3306/webvideo?useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai, UserName=root@localhost, MySQL Connector/J] will not be managed by Spring
==> Preparing: select 'true' as QUERYID, id, username, password, identity from users WHERE ( username = ? and password = ? )
==> Parameters: first(String), 9608a82e5a0fb219ccb2(String)
<== Columns: QUERYID, id, username, password, identity
<== Row: true, 2, first, 9608a82e5a0fb219ccb2, 0
<== Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@367b1aaa]
TokenMapper里的SQL执行日志
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6ee175ad] was not registered for synchronization because synchronization is not active
JDBC Connection [jdbc:mysql://localhost:3306/webvideo?useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai, UserName=root@localhost, MySQL Connector/J] will not be managed by Spring
==> Preparing: select 'true' as QUERYID, id, userId, token, applyTime, expireTime, countAuth, maxCountAuth, ussAge from tokens WHERE ( token = ? )
==> Parameters: 1699082hYIbC1166E99l41E6266106(String)
<== Columns: QUERYID, id, userId, token, applyTime, expireTime, countAuth, maxCountAuth, ussAge
<== Row: true, 48, 2, 1699082hYIbC1166E99l41E6266106, 2023-11-04 15:17:46, 2023-12-04 15:17:46, 0, 1000, default
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6ee175ad]
输出完这个日志后，代码就不继续往下跑了。
顺便说一下，执行TokenMapper里的插入操作的语句执行起来是正常的，就是查询操作的语句有问题。
根据你提供的信息，问题可能出现在TokenMapper.xml中的SQL语句或者返回结果的处理上。以下是几个可能导致问题的原因和解决方法：
1. SQL语句错误：请确保TokenMapper.xml中的SQL语句正确无误。你可以尝试在数据库客户端执行相同的SQL语句，看是否能够正常返回结果。
2. 参数问题：确认tokenExample对象中的值是正确设置的，以确保查询条件正确。你可以尝试在日志输出前打印tokenExample的参数值，以确认是否匹配到预期的记录。
3. 返回结果问题：检查TokenMapper.xml中的resultMap是否正确映射了数据库返回的字段到实体类的属性。确保实体类的属性类型与数据库字段类型相匹配。
4. 空指针异常：如果代码在查询到记录后立即停止，可能是由于返回的结果集（theToken）为空导致的空指针异常。在调用theToken.get(0)之前，可以添加对结果集是否为空的判断，例如：
```java
if (theToken != null && theToken.size() > 0) {
return theToken.get(0);
} else {
return null; // 或者抛出异常或其他处理方式
}
通过以上几个方面的排查，你应该能够找到问题所在并进行修复。如果问题仍然存在，建议提供更多的错误信息和代码细节，以便更好地帮助你。