Spring +Mybatis 拦截器配置

mybatis-config.xml

page

import java.util.ArrayList;
import java.util.List;

import org.apache.ibatis.session.RowBounds;

/**
 * Mybatis - 分页对象
 *
 * @author liuzh/abel533/isea533
 * @version 3.2.1
 * @url http://git.oschina.net/free/Mybatis_PageHelper
 */
public class Page extends ArrayList {
    /**
     * 不进行count查询
     */
    public static final int NO_SQL_COUNT = -1;
    public static final int SQL_COUNT = 0;
    private int pageNum;
    private int pageSize;
    private int startRow;
    private int endRow;
    private long total;
    private int pages;

    public Page(int pageNum, int pageSize) {
        this(pageNum, pageSize, SQL_COUNT);
    }

    public Page(int pageNum, int pageSize, int total) {
        super(pageSize);
        this.pageNum = pageNum;
        this.pageSize = pageSize;
        this.total = total;
        this.startRow = pageNum > 0 ? (pageNum - 1) * pageSize : 0;
        this.endRow = pageNum * pageSize;
    }

    public Page(RowBounds rowBounds, int total) {
        super(rowBounds.getLimit());
        this.pageSize = rowBounds.getLimit();
        this.startRow = rowBounds.getOffset();
        //RowBounds方式默认不求count总数，如果想求count,可以修改这里为SQL_COUNT
        this.total = total;
        this.endRow = this.startRow + this.pageSize;
    }

    public List getResult() {
        return this;
    }

    public int getPages() {
        return pages;
    }

    public void setPages(int pages) {
        this.pages = pages;
    }

    public int getEndRow() {
        return endRow;
    }

    public void setEndRow(int endRow) {
        this.endRow = endRow;
    }

    public int getPageNum() {
        return pageNum;
    }

    public void setPageNum(int pageNum) {
        this.pageNum = pageNum;
    }

    public int getPageSize() {
        return pageSize;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    public int getStartRow() {
        return startRow;
    }

    public void setStartRow(int startRow) {
        this.startRow = startRow;
    }

    public long getTotal() {
        return total;
    }

    public void setTotal(long total) {
        this.total = total;
    }

    @Override
    public String toString() {
        return "Page{" +
                "pageNum=" + pageNum +
                ", pageSize=" + pageSize +
                ", startRow=" + startRow +
                ", endRow=" + endRow +
                ", total=" + total +
                ", pages=" + pages +
                '}';
    }
}

import java.util.ArrayList;
import java.util.List;
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.ResultMap;
import org.apache.ibatis.mapping.ResultMapping;
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.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;


@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 localPage = new ThreadLocal();

	private static final List EMPTY_RESULTMAPPING = new ArrayList(
			0);

	// 数据库方言
	private static String dialect = "";
	// RowBounds参数offset作为PageNum使用 - 默认不使用
	private static boolean offsetAsPageNum = false;
	// RowBounds是否进行count查询 - 默认不查询
	private static boolean rowBoundsWithCount = false;

	/**
	 * 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 {
		
		System.out.println("page");
		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) {
				if (offsetAsPageNum) {
					page = new Page(rowBounds.getOffset(),
							rowBounds.getLimit(),
							rowBoundsWithCount ? Page.SQL_COUNT
									: Page.NO_SQL_COUNT);
				} else {
					page = new Page(rowBounds,
							rowBoundsWithCount ? Page.SQL_COUNT
									: Page.NO_SQL_COUNT);
				}
			}
			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 = SystemMetaObject.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());
				// 执行分页查询
				Object result = invocation.proceed();
				// 得到处理结果
				page.addAll((List) result);
				// 返回结果
				return page;
			}
		}
	}

	/**
	 * 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 + ") 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("postgresql".equals(dialect)) {
			pageSql.append(sql);
			pageSql.append(" limit " + page.getPageSize() + " offset "
					+ page.getStartRow());
		} else 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;
		}
	}

	/**
	 * 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 resultMaps = new ArrayList();
		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("")) {
			throw new RuntimeException("Mybatis分页插件PageHelper无法获取dialect参数!");
		}
		// offset作为PageNum使用
		String offset = p.getProperty("offsetAsPageNum");
		if (offset != null && offset.toUpperCase().equals("TRUE")) {
			offsetAsPageNum = true;
		}
		// RowBounds方式是否做count查询
		String withcount = p.getProperty("rowBoundsWithCount");
		if (withcount != null && withcount.toUpperCase().equals("TRUE")) {
			rowBoundsWithCount = true;
		}
	}
}

用法：

public String getUserList(HttpServletRequest request) {
		String json = "";
		try {
			String page = request.getParameter("page");
			String rows = request.getParameter("rows");
			
			// 开始分页
			PageHelper.startPage(Integer.parseInt(page), Integer.parseInt(rows));
			
			List> mapList = userDao.getUserList(null);
			
			Map map = new HashMap(); 
			map.put("total", ((Page>)mapList).getTotal());
			map.put("rows", mapList);
			
			json = JSONObject.fromObject(map).toString();
		} catch (Exception e) {
			e.printStackTrace();
		}
		return json;
	}