SSM框架 Mybatis项目示例代码

package com.wporoad.app.util; 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.SystemMetaObject; import org.apache.ibatis.session.ResultHandler; import org.apache.ibatis.session.RowBounds; import javax.xml.bind.PropertyException; import java.util.ArrayList; import java.util.List; import java.util.Properties; /** * Mybatis - 通用分页拦截器v3.1.0 * * @author liuzh/abel533/isea * Created by liuzh on 14-4-15. * Update by liuzh on 14-5-20. * Update by liuzh on 14-5-21. */ @Intercepts(@Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class})) public class PageHelper implements Interceptor { private static final ThreadLocal<Page> localPage = new ThreadLocal<Page>(); private static final List<ResultMapping> EMPTY_RESULTMAPPING = new ArrayList<ResultMapping>(0); private static String dialect = ""; //数据库方言 /** * 开始分页 * * @param pageNum * @param pageSize */ public static void startPage(int pageNum, int pageSize) { startPage(pageNum, pageSize, true); } /** * 开始分页 * * @param pageNum * @param pageSize */ public static void startPage(int pageNum, int pageSize, boolean count) { localPage.set(new Page(pageNum, pageSize, count? Page.SQL_COUNT: Page.NO_SQL_COUNT)); } @Override public Object intercept(Invocation invocation) throws Throwable { final Object[] args = invocation.getArgs(); RowBounds rowBounds = (RowBounds)args[2]; if (localPage.get() == null && rowBounds == RowBounds.DEFAULT) { return invocation.proceed(); } else { //忽略RowBounds-否则会进行Mybatis自带的内存分页 args[2] = RowBounds.DEFAULT; MappedStatement ms = (MappedStatement) args[0]; Object parameterObject = args[1]; BoundSql boundSql = ms.getBoundSql(parameterObject); //分页信息 Page page = localPage.get(); //移除本地变量 localPage.remove(); if (page == null) { page = new Page(rowBounds); } MappedStatement qs = newMappedStatement(ms, new BoundSqlSqlSource(boundSql)); //将参数中的MappedStatement替换为新的qs，防止并发异常 args[0] = qs; MetaObject msObject = MetaObject.forObject(qs); String sql = (String) msObject.getValue("sqlSource.boundSql.sql"); //简单的通过total的值来判断是否进行count查询 if (page.getTotal() > Page.NO_SQL_COUNT) { //求count - 重写sql msObject.setValue("sqlSource.boundSql.sql", getCountSql(sql)); //查询总数 Object result = invocation.proceed(); int totalCount = (Integer)((List) result).get(0); page.setTotal(totalCount); int totalPage = totalCount / page.getPageSize() + ((totalCount % page.getPageSize() == 0) ? 0 : 1); page.setPages(totalPage); //分页sql - 重写sql msObject.setValue("sqlSource.boundSql.sql", getPageSql(sql, page)); //恢复类型 msObject.setValue("resultMaps", ms.getResultMaps()); //执行分页查询 result = invocation.proceed(); //得到处理结果 page.addAll((List) result); //返回结果 return page; } else { //分页sql - 重写sql msObject.setValue("sqlSource.boundSql.sql", getPageSql(sql, page)); //恢复类型 msObject.setValue("resultMaps", ms.getResultMaps()); //返回结果 return invocation.proceed(); } } } /** * 获取总数sql - 如果要支持其他数据库，修改这里就可以 * @param sql * @return */ private String getCountSql(String sql) { return "select count(0) from (" + sql + ") as tmp_count"; } /** * 获取分页sql - 如果要支持其他数据库，修改这里就可以 * @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("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; } } /** * 由于MappedStatement是一个全局共享的对象，因而需要复制一个对象来进行操作，防止并发访问导致错误 * * @param ms * @param newSqlSource * @return */ private MappedStatement newMappedStatement(MappedStatement ms, SqlSource newSqlSource) { MappedStatement.Builder builder = new MappedStatement.Builder(ms.getConfiguration(), ms.getId() + "_分页", 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) { StringBuffer keyProperties = new StringBuffer(); 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()); //由于resultMaps第一次需要返回int类型的结果，所以这里需要生成一个resultMap - 防止并发错误 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(); } /** * 只拦截Executor * * @param target * @return */ @Override public Object plugin(Object target) { if (target instanceof Executor) { return Plugin.wrap(target, this); } else { return target; } } public void setProperties(Properties p) { dialect = p.getProperty("dialect"); if (dialect!=null&&dialect.equals("")) { try { throw new PropertyException("dialect propert