Java tutorial
package com.jeeplus.weixin.common.pagination;/* The MIT License (MIT) Copyright (c) 2014 abel533@gmail.com Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ import org.apache.ibatis.executor.Executor; import org.apache.ibatis.mapping.*; import org.apache.ibatis.plugin.*; import org.apache.ibatis.reflection.MetaObject; import org.apache.ibatis.reflection.factory.DefaultObjectFactory; import org.apache.ibatis.reflection.factory.ObjectFactory; import org.apache.ibatis.reflection.wrapper.DefaultObjectWrapperFactory; import org.apache.ibatis.reflection.wrapper.ObjectWrapperFactory; import org.apache.ibatis.session.ResultHandler; import org.apache.ibatis.session.RowBounds; import java.util.ArrayList; import java.util.List; import java.util.Properties; /** * Mybatis - * * @author liuzh/abel533/isea533 * @version 3.2.2 * @url http://git.oschina.net/free/Mybatis_PageHelper */ @Intercepts(@Signature(type = Executor.class, method = "query", args = { MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class })) public class PageHelper implements Interceptor { public static final ObjectFactory DEFAULT_OBJECT_FACTORY = new DefaultObjectFactory(); public static final ObjectWrapperFactory DEFAULT_OBJECT_WRAPPER_FACTORY = new DefaultObjectWrapperFactory(); public static final MetaObject NULL_META_OBJECT = MetaObject.forObject(NullObject.class, DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY); private static class NullObject { } /** * ??Mybatis? * @param object * @return */ public static MetaObject forObject(Object object) { return MetaObject.forObject(object, DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY); } private static final String BOUND_SQL = "sqlSource.boundSql.sql"; private static final ThreadLocal<Page> LOCAL_PAGE = new ThreadLocal<Page>(); private static final List<ResultMapping> EMPTY_RESULTMAPPING = new ArrayList<ResultMapping>(0); //? private static String dialect = ""; //RowBounds?offsetPageNum - ? private static boolean offsetAsPageNum = false; //RowBounds?count - ? private static boolean rowBoundsWithCount = false; /** * * * @param pageNum * @param pageSize */ public static void startPage(int pageNum, int pageSize) { startPage(pageNum, pageSize, true); } /** * * * @param pageNum * @param pageSize */ public static void startPage(int pageNum, int pageSize, boolean count) { LOCAL_PAGE.set(new Page(pageNum, pageSize, count)); } /** * ?? * * @param rowBounds * @return */ private Page getPage(RowBounds rowBounds) { Page page = LOCAL_PAGE.get(); //?? LOCAL_PAGE.remove(); if (page == null) { if (offsetAsPageNum) { page = new Page(rowBounds.getOffset(), rowBounds.getLimit(), rowBoundsWithCount); } else { page = new Page(rowBounds, rowBoundsWithCount); } } return page; } /** * Mybatis * * @param invocation * @return * @throws Throwable */ @Override public Object intercept(Invocation invocation) throws Throwable { final Object[] args = invocation.getArgs(); RowBounds rowBounds = (RowBounds) args[2]; if (LOCAL_PAGE.get() == null && rowBounds == RowBounds.DEFAULT) { return invocation.proceed(); } else { //RowBounds-?Mybatis args[2] = RowBounds.DEFAULT; MappedStatement ms = (MappedStatement) args[0]; Object parameterObject = args[1]; BoundSql boundSql = ms.getBoundSql(parameterObject); //? Page page = getPage(rowBounds); //MappedStatement MappedStatement qs = newMappedStatement(ms, new BoundSqlSqlSource(boundSql)); //?MappedStatement?qs? args[0] = qs; MetaObject msObject = forObject(qs); String sql = (String) msObject.getValue(BOUND_SQL); //?total??count if (page.isCount()) { //count - ?sql msObject.setValue(BOUND_SQL, getCountSql(sql)); // Object result = invocation.proceed(); // page.setTotal((Integer) ((List) result).get(0)); } //sql - ?sql msObject.setValue(BOUND_SQL, getPageSql(sql, page)); //?? msObject.setValue("resultMaps", ms.getResultMaps()); // Object result = invocation.proceed(); //? page.addAll((List) result); // return page; } } /** * ?sql - ???? * * @param sql * @return */ private String getCountSql(String sql) { int index = sql.indexOf("from"); return "select count(0) " + sql.substring(index); } /** * ?sql - ???? * * @param sql * @param page * @return */ private String getPageSql(String sql, Page page) { StringBuilder pageSql = new StringBuilder(200); if ("mysql".equals(dialect)) { pageSql.append(sql); pageSql.append(" limit " + page.getStartRow() + "," + page.getPageSize()); } else if ("hsqldb".equals(dialect)) { pageSql.append(sql); pageSql.append(" LIMIT " + page.getPageSize() + " OFFSET " + page.getStartRow()); } else if ("oracle".equals(dialect)) { pageSql.append("select * from ( select temp.*, rownum row_id from ( "); pageSql.append(sql); pageSql.append(" ) temp where rownum <= ").append(page.getEndRow()); pageSql.append(") where row_id > ").append(page.getStartRow()); } return pageSql.toString(); } private class BoundSqlSqlSource implements SqlSource { BoundSql boundSql; public BoundSqlSqlSource(BoundSql boundSql) { this.boundSql = boundSql; } public BoundSql getBoundSql(Object parameterObject) { return boundSql; } } /** * MappedStatement????? * * @param ms * @param newSqlSource * @return */ private MappedStatement newMappedStatement(MappedStatement ms, SqlSource newSqlSource) { MappedStatement.Builder builder = new MappedStatement.Builder(ms.getConfiguration(), ms.getId() + "_PageHelper", newSqlSource, ms.getSqlCommandType()); builder.resource(ms.getResource()); builder.fetchSize(ms.getFetchSize()); builder.statementType(ms.getStatementType()); builder.keyGenerator(ms.getKeyGenerator()); if (ms.getKeyProperties() != null && ms.getKeyProperties().length != 0) { StringBuilder keyProperties = new StringBuilder(); for (String keyProperty : ms.getKeyProperties()) { keyProperties.append(keyProperty).append(","); } keyProperties.delete(keyProperties.length() - 1, keyProperties.length()); builder.keyProperty(keyProperties.toString()); } builder.timeout(ms.getTimeout()); builder.parameterMap(ms.getParameterMap()); //resultMaps?int??resultMap - ? List<ResultMap> resultMaps = new ArrayList<ResultMap>(); ResultMap resultMap = new ResultMap.Builder(ms.getConfiguration(), ms.getId(), int.class, EMPTY_RESULTMAPPING).build(); resultMaps.add(resultMap); builder.resultMaps(resultMaps); builder.resultSetType(ms.getResultSetType()); builder.cache(ms.getCache()); builder.flushCacheRequired(ms.isFlushCacheRequired()); builder.useCache(ms.isUseCache()); return builder.build(); } /** * ?Executor * * @param target * @return */ @Override public Object plugin(Object target) { if (target instanceof Executor) { return Plugin.wrap(target, this); } else { return target; } } /** * * * @param p */ public void setProperties(Properties p) { dialect = p.getProperty("dialect"); if (dialect == null || "".equals(dialect)) { throw new RuntimeException("Mybatis?PageHelper?dialect?!"); } //offsetPageNum String offset = p.getProperty("offsetAsPageNum"); if (offset != null && "TRUE".equalsIgnoreCase(offset)) { offsetAsPageNum = true; } //RowBounds???count String withcount = p.getProperty("rowBoundsWithCount"); if (withcount != null && "TRUE".equalsIgnoreCase(withcount)) { rowBoundsWithCount = true; } } }