mybits拦截器实现分页

1.page类

**
 * Created by wyp on 2017/11/17.
 * 分页使用参数
 */
public interface PageConstants {
//    public static final String SHOW_COUNT_KEY = "showCount" ; // 每页显示记录数的key
//    public static final  String CURRENT_PAGE_KEY = "currentPage";//当前页
    public static final String SHOW_COUNT_KEY = "rows" ; // 每页显示记录数的key
    public static final  String CURRENT_PAGE_KEY = "page";//当前页
    public static final  String TOTAL_PAGE_KEY = "totalPage";//总页数
    public static final String TOTAL_RESULT_KEY = "totalResult";//总记录数
    public static final  String  CURRENT_RESULT_KEY = "currentResult"; // 当前记录起始索引

    //初始化当前页
    public static final Integer INIT_CURRENT_PAGE = 1;
    //初始化每页显示的个数
    public static final Integer INIT_SHOW_COUNT=20;

    /**
     * 通过总数量和显示个数计算总页数
     * @param totalResult
     * @param showCount
     * @return
     */
    public static int getTotalPage(Integer totalResult,Integer showCount) {
        int totalPage = 0;
        if (totalResult % showCount == 0)
            totalPage = totalResult / showCount;
        else
            totalPage = totalResult / showCount + 1;
        return totalPage;
    }

    /**
     * 获取当前结果
     * @param currentPage
     * @param showCount
     * @return
     */
    public static int getCurrentResult(Integer currentPage,Integer showCount ) {

        int currentResult = (currentPage - 1) * showCount;
        if (currentResult < 0)
            currentResult = 0;
        return currentResult;
    }

}

2.mybits分页拦截PagePlugin

/**
 * 
 * 类名称：PagePlugin.java 类描述：
 * 
 * @version 1.0
 * @Intercepts 是mybaits的拦截器注解
 * @Signature 表明要拦截的接口、方法以及对应的参数类型。
 */
@Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class ,Integer.class}) })
public class PagePlugin implements Interceptor {

   private static String dialect = ""; // 数据库方言
   private static String pageSqlId = ""; // mapper.xml中需要拦截的ID(正则匹配)

   public Object intercept(Invocation ivk) throws Throwable {
      if (ivk.getTarget() instanceof RoutingStatementHandler) {
         RoutingStatementHandler statementHandler = (RoutingStatementHandler) ivk.getTarget();
         BaseStatementHandler delegate = (BaseStatementHandler) ReflectHelper.getValueByFieldName(statementHandler,
               "delegate");
         MappedStatement mappedStatement = (MappedStatement) ReflectHelper.getValueByFieldName(delegate,
               "mappedStatement");

         if (mappedStatement.getId().matches(pageSqlId)) { // 拦截需要分页的SQL
            BoundSql boundSql = delegate.getBoundSql();
            // 分页SQL<select>中parameterType属性对应的实体参数，即Mapper接口中执行分页方法的参数,该参数不得为空
            Object parameterObject = boundSql.getParameterObject();
            if (parameterObject == null) {
               throw new NullPointerException("parameterObject尚未实例化！");
            } else {
               Connection connection = (Connection) ivk.getArgs()[0];
               String sql = boundSql.getSql();
               // String countSql = "select count(0) from (" + sql+ ") as
               // tmp_count"; //记录统计
               String countSql = "select count(0) from (" + sql + ")  tmp_count"; // 记录统计
                                                                  // ==
                                                                  // oracle
                                                                  // 加
                                                                  // as
                                                                  // 报错(SQL
                                                                  // command
                                                                  // not
                                                                  // properly
                                                                  // ended)
               PreparedStatement countStmt = connection.prepareStatement(countSql);
               BoundSql countBS = new BoundSql(mappedStatement.getConfiguration(), countSql,
                     boundSql.getParameterMappings(), parameterObject);
               setParameters(countStmt, mappedStatement, countBS, parameterObject);
               ResultSet rs = countStmt.executeQuery();
               int count = 0;
               if (rs.next()) {
                  count = rs.getInt(1);
               }
               rs.close();
               countStmt.close();
               // System.out.println(count);
               ParameterMap parameMap = null;
               if(parameterObject instanceof ParameterMap){
                  parameMap = (ParameterMap) parameterObject;
                  doPageParm(parameMap,count);
               }
               String pageSql = generatePageSql(sql, parameMap);
               ReflectHelper.setValueByFieldName(boundSql, "sql", pageSql); // 将分页sql语句反射回BoundSql.
            }
         }
      }
      return ivk.proceed();
   }

   /**
    * 将总记录数封装到参数里面
    * @param parameterMap
    * @param count 总数
     */
   public void doPageParm(ParameterMap parameterMap ,int count){
         //如果总页数
         Object shwoCount = parameterMap.get(PageConstants.SHOW_COUNT_KEY);
         Integer show = PageConstants.INIT_SHOW_COUNT;
         if(shwoCount!=null&&StringUtils.isNumeric(String.valueOf(show))){
            show = Integer.parseInt(String.valueOf(shwoCount));
         }
         parameterMap.put(PageConstants.SHOW_COUNT_KEY,show);
         Integer currentPage = PageConstants.INIT_CURRENT_PAGE;
         Object curreantString = parameterMap.get(PageConstants.CURRENT_PAGE_KEY);
         if(curreantString!=null&&StringUtils.isNumeric(String.valueOf(curreantString))){
            currentPage = Integer.parseInt(String.valueOf(curreantString));
         }
         parameterMap.put(PageConstants.CURRENT_PAGE_KEY,currentPage);

         //总页数
         Integer totalPage = PageConstants.getTotalPage(count, show);
         parameterMap.put(PageConstants.TOTAL_PAGE_KEY,totalPage);
         //当前索引号
         Integer currentResult = PageConstants.getCurrentResult(currentPage, show);
         parameterMap.put(PageConstants.CURRENT_RESULT_KEY,currentResult);
         //总记录数
         parameterMap.put(PageConstants.TOTAL_RESULT_KEY,count);

   }


   /**
    * 对SQL参数(?)设值,参考org.apache.ibatis.executor.parameter.DefaultParameterHandler
    * 
    * @param ps
    * @param mappedStatement
    * @param boundSql
    * @param parameterObject
    * @throws SQLException
    */
   @SuppressWarnings({ "rawtypes", "unchecked" })
   private void setParameters(PreparedStatement ps, MappedStatement mappedStatement, BoundSql boundSql,
         Object parameterObject) throws SQLException {
      ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());
      List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
      if (parameterMappings != null) {
         Configuration configuration = mappedStatement.getConfiguration();
         TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();
         MetaObject metaObject = parameterObject == null ? null : configuration.newMetaObject(parameterObject);
         for (int i = 0; i < parameterMappings.size(); i++) {
            ParameterMapping parameterMapping = parameterMappings.get(i);
            if (parameterMapping.getMode() != ParameterMode.OUT) {
               Object value;
               String propertyName = parameterMapping.getProperty();
               PropertyTokenizer prop = new PropertyTokenizer(propertyName);
               if (parameterObject == null) {
                  value = null;
               } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
                  value = parameterObject;
               } else if (boundSql.hasAdditionalParameter(propertyName)) {
                  value = boundSql.getAdditionalParameter(propertyName);
               } else if (propertyName.startsWith(ForEachSqlNode.ITEM_PREFIX)
                     && boundSql.hasAdditionalParameter(prop.getName())) {
                  value = boundSql.getAdditionalParameter(prop.getName());
                  if (value != null) {
                     value = configuration.newMetaObject(value)
                           .getValue(propertyName.substring(prop.getName().length()));
                  }
               } else {
                  value = metaObject == null ? null : metaObject.getValue(propertyName);
               }
               TypeHandler typeHandler = parameterMapping.getTypeHandler();
               if (typeHandler == null) {
                  throw new ExecutorException("There was no TypeHandler found for parameter " + propertyName
                        + " of statement " + mappedStatement.getId());
               }
               typeHandler.setParameter(ps, i + 1, value, parameterMapping.getJdbcType());
            }
         }
      }
   }

   /**
    * 根据数据库方言，生成特定的分页sql
    * 
    * @param sql
    * @param parameMap
    * @return
    */
   private String generatePageSql(String sql, ParameterMap parameMap) {
      if (parameMap != null && Tools.notEmpty(dialect)) {
         StringBuffer pageSql = new StringBuffer();
         if ("mysql".equals(dialect)) {
            pageSql.append(sql);
            pageSql.append(" limit " +parameMap.get(PageConstants.CURRENT_RESULT_KEY) + "," + parameMap.get(PageConstants.SHOW_COUNT_KEY));
         } else if ("oracle".equals(dialect)) {
            pageSql.append("select * from (select tmp_tb.*,ROWNUM row_id from (");
            pageSql.append(sql);
            // pageSql.append(") as tmp_tb where ROWNUM<=");
            pageSql.append(") tmp_tb where ROWNUM<=");
            pageSql.append(parameMap.get(PageConstants.CURRENT_RESULT_KEY)).append("+").append( parameMap.get(PageConstants.SHOW_COUNT_KEY));
            pageSql.append(") where row_id>");
            pageSql.append(parameMap.get(PageConstants.CURRENT_RESULT_KEY));
         }
         return pageSql.toString();
      } else {
         return sql;
      }
   }

   public Object plugin(Object arg0) {
      return Plugin.wrap(arg0, this);
   }

   public void setProperties(Properties p) {
      dialect = p.getProperty("dialect");
      if (Tools.isEmpty(dialect)) {
         try {
            throw new PropertyException("dialect property is not found!");
         } catch (PropertyException e) {
            e.printStackTrace();
         }
      }
      pageSqlId = p.getProperty("pageSqlId");
      if (Tools.isEmpty(pageSqlId)) {
         try {
            throw new PropertyException("pageSqlId property is not found!");
         } catch (PropertyException e) {
            e.printStackTrace();
         }
      }
   }

}

3.mybits-config.xml增加拦截配置，拦截所有Page结尾的mybits方法。

<plugins>
   <plugin interceptor="com.lrs.admin.plugin.PagePlugin">
      <property name="dialect" value="mysql"/>
      <property name="pageSqlId" value=".*Page.*"/>
   </plugin>
</plugins>

4.分页信息放入map集合中，前段配合jqgrid表格分页使用更方便。