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

Question

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);


```的时候，能正确查询到数据库里的记录然后赋值到user。但是在TokenServiceImpl.java里执行
```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。
求解答，搞一天了还没解决这问题

Answer 1

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根据提供的代码和日志，报错提示是因为没有激活同步功能而导致的。解决方案如下：

1. 在Spring配置文件中，确保已激活事务管理器。可以使用以下代码片段：

   <tx:annotation-driven/>
   

2. 在TokenServiceImpl类上添加@Transactional注解，以确保在该类中的所有方法都处于同一个事务中。例如：

   @Service
   @Transactional
   public class TokenServiceImpl implements TokenService {
     //...
   }
   

3. 确保在方法上使用@Transactional注解，以确保方法在事务中执行。例如：

   @Override
   @Transactional
   public void addToken(Token token) {
     tokenMapper.insert(token);
   }
   

请注意，以上解决方案假设您在项目中使用了Spring事务管理器来管理数据库事务。如果您没有使用事务管理器或使用了其他的事务管理方式，请根据实际情况调整解决方案。