分頁插件在MyBatis中的自定義實(shí)現(xiàn)

要在MyBatis中自定義分頁插件，需要實(shí)現(xiàn)org.apache.ibatis.plugin.Interceptor接口，并重寫它的intercept方法。該方法用于攔截Executor中的查詢方法，實(shí)現(xiàn)分頁功能。

首先，創(chuàng)建一個(gè)自定義的分頁插件類，實(shí)現(xiàn)Interceptor接口，并重寫intercept方法。在intercept方法中，可以獲取到執(zhí)行的Statement對(duì)象和參數(shù)，然后根據(jù)參數(shù)中的分頁信息對(duì)查詢結(jié)果進(jìn)行分頁處理。

public class MyPageInterceptor implements Interceptor {

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        // 獲取執(zhí)行的方法
        Method method = invocation.getMethod();
        // 獲取方法參數(shù)
        Object[] args = invocation.getArgs();

        // 獲取Statement對(duì)象
        StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
        BoundSql boundSql = statementHandler.getBoundSql();
        Configuration configuration = statementHandler.getConfiguration();
        MappedStatement mappedStatement = (MappedStatement) ReflectUtil.getFieldValue(statementHandler, "mappedStatement");

        // 獲取分頁信息
        PageParam page = PageParamHolder.get();
        if (page != null) {
            // 構(gòu)建分頁查詢 SQL
            String sql = boundSql.getSql();
            String countSql = "select count(0) from (" + sql + ") as total";
            Connection connection = (Connection) invocation.getArgs()[0];
            PreparedStatement countStatement = connection.prepareStatement(countSql);
            BoundSql countBoundSql = new BoundSql(configuration, countSql, boundSql.getParameterMappings(), boundSql.getParameterObject());
            ParameterHandler parameterHandler = new DefaultParameterHandler(mappedStatement, boundSql.getParameterObject(), countBoundSql);
            parameterHandler.setParameters(countStatement);
            ResultSet rs = countStatement.executeQuery();
            if (rs.next()) {
                page.setTotal(rs.getInt(1));
            }
            rs.close();
            countStatement.close();

            // 構(gòu)建分頁 SQL
            String pageSql = sql + " limit " + page.getStart() + "," + page.getSize();
            ReflectUtil.setFieldValue(boundSql, "sql", pageSql);
        }

        return invocation.proceed();
    }

    @Override
    public Object plugin(Object target) {
        return Plugin.wrap(target, this);
    }

    @Override
    public void setProperties(Properties properties) {
    }
}

然后，將自定義的分頁插件注冊(cè)到MyBatis的配置中，并配置需要攔截的方法?？梢栽贛yBatis的配置文件中添加如下配置：

<plugins>
    <plugin interceptor="com.example.MyPageInterceptor">
        <property name="someProperty" value="100"/>
    </plugin>
</plugins>

這樣就完成了在MyBatis中自定義實(shí)現(xiàn)分頁插件的過程。通過這個(gè)自定義的分頁插件，可以方便地對(duì)查詢結(jié)果進(jìn)行分頁處理。