org.nebula.service.dao.PaginationInterceptor.java Source code

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Here is the source code for org.nebula.service.dao.PaginationInterceptor.java

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/*
 * Copyright 2002-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.nebula.service.dao;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.lang.reflect.FieldUtils;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.session.RowBounds;
import org.apache.log4j.Logger;

import java.sql.Connection;
import java.util.Properties;
import java.util.regex.Pattern;

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

    private final static Logger logger = Logger.getLogger(PaginationInterceptor.class);
    private final static String SQL_SELECT_REGEX = "(?is)^\\s*SELECT.*$";
    private final static String SQL_COUNT_REGEX = "(?is)^\\s*SELECT\\s+COUNT\\s*\\(\\s*(?:\\*|\\w+)\\s*\\).*$";

    // @Override
    public Object intercept(Invocation inv) throws Throwable {

        StatementHandler target = (StatementHandler) inv.getTarget();
        BoundSql boundSql = target.getBoundSql();
        String sql = boundSql.getSql();
        if (StringUtils.isBlank(sql)) {
            return inv.proceed();
        }
        logger.debug("origin sql>>>>>" + sql.replaceAll("\n", ""));
        // ?select??
        if (sql.matches(SQL_SELECT_REGEX) && !Pattern.matches(SQL_COUNT_REGEX, sql)) {
            Object obj = FieldUtils.readField(target, "delegate", true);
            // ??? RowBounds 
            RowBounds rowBounds = (RowBounds) FieldUtils.readField(obj, "rowBounds", true);
            // ??SQL
            if (rowBounds != null && rowBounds != RowBounds.DEFAULT) {
                FieldUtils.writeField(boundSql, "sql", newSql(sql, rowBounds), true);
                logger.debug("new sql>>>>>" + boundSql.getSql().replaceAll("\n", ""));
                // ???(?)
                FieldUtils.writeField(rowBounds, "offset", RowBounds.NO_ROW_OFFSET, true);
                FieldUtils.writeField(rowBounds, "limit", RowBounds.NO_ROW_LIMIT, true);
            }
        }
        return inv.proceed();
    }

    public String newSql(String oldSql, RowBounds rowBounds) {
        return getLimitString(oldSql, rowBounds.getOffset(), Integer.toString(rowBounds.getOffset()),
                Integer.toString(rowBounds.getLimit()));
    }

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

    // @Override
    public void setProperties(Properties arg0) {

    }

    private String getLimitString(String sql, int offset, String offsetPlaceholder, String limitPlaceholder) {
        StringBuilder stringBuilder = new StringBuilder(sql);
        stringBuilder.append(" limit ");
        if (offset > 0) {
            stringBuilder.append(offsetPlaceholder).append(",").append(limitPlaceholder);
        } else {
            stringBuilder.append(limitPlaceholder);
        }
        return stringBuilder.toString();
    }

}