关于springboot:springbootmybatis拦截器不生效问题分析

一、环境信息
SpringBoot:2.3.6.RELEASE
Mybatis-plus:3.3.1
二、碰到问题
明天因业务零碎性能须要，应用mybatis的拦截器对ORACLE的数据库会话进行用户以后语言环境设置(NLS_LANGUAGE),碰到拦截器代码不失效的问题，特此记录下来，不便未来查阅。
三、代码如下：
1、在Mybatis的@Configuration相干代码增加如下代码（主动注入到拦截器链）：

/** * 更改会话状态 * * @return */@Beanpublic AlterSessionInterceptor alterSessionInterceptor() {    return new AlterSessionInterceptor();}

2、拦截器代码（拦挡StatementHandler的prepare办法，取到Connection执行ALTER SESSION的语句）：
/**

• <p>
• 更改会话解析器
• </p>
  *
• @since 2021/7/14
  */

@Slf4j
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class AlterSessionInterceptor implements Interceptor {

@Overridepublic Object intercept(Invocation invocation) throws Throwable {    Object[] args = invocation.getArgs();    Connection connection = (Connection) args[0];    if ("Oracle".equalsIgnoreCase(connection.getMetaData().getDatabaseProductName())) {        Statement statement = null;        try {            statement = connection.createStatement();            String locale = RequestHelper.getCurrentLocale();            if ("en_GB".equalsIgnoreCase(locale)) {                statement.execute("ALTER SESSION SET NLS_LANGUAGE='AMERICAN'");            } else {                statement.execute("ALTER SESSION SET NLS_LANGUAGE='SIMPLIFIED CHINESE'");            }        } finally {            statement.close();        }    }    return invocation.proceed();}

}
在运行调试时发现代码无奈执行到拦挡逻辑，通过参考分页插件代码，发现须要重载以下办法（代码默认是只有实现intercept这个接口，然而实际上须要多加以下插件的解决逻辑才能够，才会启用Plugin的Proxy）：

@Overridepublic Object plugin(Object target) {    if (target instanceof StatementHandler) {        return Plugin.wrap(target, this);    }    return target;}

最终拦截器代码如下：
/**

• <p>
• 更改会话解析器
• </p>
  *
• @since 2021/7/14
  */

@Slf4j
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class AlterSessionInterceptor implements Interceptor {

@Overridepublic Object intercept(Invocation invocation) throws Throwable {    Object[] args = invocation.getArgs();    Connection connection = (Connection) args[0];    if ("Oracle".equalsIgnoreCase(connection.getMetaData().getDatabaseProductName())) {        Statement statement = null;        try {            statement = connection.createStatement();            String locale = RequestHelper.getCurrentLocale();            if ("en_GB".equalsIgnoreCase(locale)) {                statement.execute("ALTER SESSION SET NLS_LANGUAGE='AMERICAN'");            } else {                statement.execute("ALTER SESSION SET NLS_LANGUAGE='SIMPLIFIED CHINESE'");            }        } finally {            statement.close();        }    }    return invocation.proceed();}@Overridepublic Object plugin(Object target) {    if (target instanceof StatementHandler) {        return Plugin.wrap(target, this);    }    return target;}@Overridepublic void setProperties(Properties properties) {    // to do nothing}

}