com.yimidida.shards.plugin.PaginationInterceptor.java Source code

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Here is the source code for com.yimidida.shards.plugin.PaginationInterceptor.java

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/*
 * @(#)PaginationInterceptor.java 2012-8-17 ?2:32:29
 *
 * Copyright (c) 2011-2012 Makersoft.org all rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 *
 */
package com.yimidida.shards.plugin;

import java.util.Properties;

import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.MappedStatement.Builder;
import org.apache.ibatis.mapping.ParameterMapping;
import org.apache.ibatis.mapping.SqlSource;
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.ResultHandler;
import org.apache.ibatis.session.RowBounds;

import com.yimidida.shards.MyBatisShardsException;
import com.yimidida.shards.plugin.spi.Dialect;

/**
 * ?.
 * <p>
 * 
 * </p>
 * 
 * <code>
 *    <plugins>
 *     <plugin interceptor="org.makersoft.shards.plugin.PaginationInterceptor">
 *         <property name="dialect" value="org.makersoft.shards.plugin.spi.impl.MySQLDialect"/>
 *     </plugin>
 *  </plugins> 
 * </code>
 * 
 * @version 2012-8-17 ?2:32:29
 * @author Feng Kuok
 */
@Intercepts({ @Signature(type = Executor.class, method = "query", args = { MappedStatement.class, Object.class,
        RowBounds.class, ResultHandler.class }) })
public class PaginationInterceptor implements Interceptor {

    static int INDEX_MAPPED_STATEMENT = 0;
    static int INDEX_PARAMETER = 1;
    static int INDEX_ROW_BOUNDS = 2;
    static int INDEX_RESULT_HANDLER = 3;

    protected Dialect dialect;

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        final MappedStatement mappedStatement = this.getMappedStatement(invocation);
        final Object parameter = this.getParameter(invocation);
        final RowBounds rowBounds = this.getRowBounds(invocation);

        final int offset = rowBounds.getOffset();
        final int limit = rowBounds.getLimit();

        if (dialect.supportLimit() && (offset != RowBounds.NO_ROW_OFFSET || limit != RowBounds.NO_ROW_LIMIT)) {
            BoundSql boundSql = mappedStatement.getBoundSql(parameter);
            String sql = boundSql.getSql().trim();

            if (dialect.supportOffsetLimit()) {
                sql = dialect.getLimitString(sql, offset, limit);
            } else {
                sql = dialect.getLimitString(sql, RowBounds.NO_ROW_OFFSET, limit);
            }

            this.setMappedStatement(invocation, this.buildMappedStatement(mappedStatement, boundSql, sql));
            this.setRowBounds(invocation, RowBounds.DEFAULT);
        }

        return invocation.proceed();
    }

    private MappedStatement buildMappedStatement(MappedStatement ms, BoundSql boundSql, String sql) {
        Builder builder = new MappedStatement.Builder(ms.getConfiguration(), ms.getId(),
                new BoundSqlSqlSource(ms, boundSql, sql), ms.getSqlCommandType());

        builder.resource(ms.getResource());
        builder.parameterMap(ms.getParameterMap());
        builder.resultMaps(ms.getResultMaps());
        builder.fetchSize(ms.getFetchSize());
        builder.timeout(ms.getTimeout());
        builder.statementType(ms.getStatementType());
        builder.resultSetType(ms.getResultSetType());
        builder.cache(ms.getCache());
        builder.flushCacheRequired(ms.isFlushCacheRequired());
        builder.useCache(ms.isUseCache());
        builder.keyGenerator(ms.getKeyGenerator());
        builder.keyProperty(delimitedArraytoString(ms.getKeyProperties()));
        builder.keyColumn(delimitedArraytoString(ms.getKeyColumns()));
        builder.databaseId(ms.getDatabaseId());

        return builder.build();
    }

    private MappedStatement getMappedStatement(Invocation invocation) {
        return (MappedStatement) invocation.getArgs()[INDEX_MAPPED_STATEMENT];
    }

    private void setMappedStatement(Invocation invocation, MappedStatement mappedStatement) {
        invocation.getArgs()[INDEX_MAPPED_STATEMENT] = mappedStatement;
    }

    private Object getParameter(Invocation invocation) {
        return invocation.getArgs()[INDEX_PARAMETER];
    }

    private RowBounds getRowBounds(Invocation invocation) {
        return (RowBounds) invocation.getArgs()[INDEX_ROW_BOUNDS];
    }

    private void setRowBounds(Invocation invocation, RowBounds rowBounds) {
        invocation.getArgs()[INDEX_ROW_BOUNDS] = rowBounds;
    }

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

    @Override
    public void setProperties(Properties properties) {
        String dialectClass = properties.getProperty("dialect");
        try {
            dialect = (Dialect) Class.forName(dialectClass).newInstance();
        } catch (Exception e) {
            throw new MyBatisShardsException("Can not create dialect instance by dialect:" + dialectClass, e);
        }
    }

    private static String delimitedArraytoString(String[] in) {
        if (in == null || in.length == 0) {
            return null;
        } else {
            StringBuffer answer = new StringBuffer();
            for (String str : in) {
                answer.append(str).append(",");
            }
            return answer.toString();
        }
    }

    public static class BoundSqlSqlSource implements SqlSource {
        private final BoundSql boundSql;

        public BoundSqlSqlSource(MappedStatement ms, BoundSql boundSql, String sql) {
            this.boundSql = buildBoundSql(ms, boundSql, sql);
        }

        public BoundSql getBoundSql(Object parameterObject) {
            return boundSql;
        }

        private BoundSql buildBoundSql(MappedStatement ms, BoundSql boundSql, String sql) {
            BoundSql newBoundSql = new BoundSql(ms.getConfiguration(), sql, boundSql.getParameterMappings(),
                    boundSql.getParameterObject());
            for (ParameterMapping mapping : boundSql.getParameterMappings()) {
                String prop = mapping.getProperty();
                if (boundSql.hasAdditionalParameter(prop)) {
                    newBoundSql.setAdditionalParameter(prop, boundSql.getAdditionalParameter(prop));
                }
            }
            return newBoundSql;
        }

    }
}