java分页拦截类实现sql自动分页

本文实例为大家分享了完整的java分页拦截类，供大家参考，具体内容如下

package com.opms.interceptor;


import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

import org.apache.ibatis.executor.parameter.ParameterHandler;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
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.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.scripting.defaults.DefaultParameterHandler;
import org.apache.ibatis.session.RowBounds;

import com.wifi.core.page.Page;


@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class})})
public class PageInterceptor implements Interceptor {
 
 private static final Log logger = LogFactory.getLog(PageInterceptor.class);
 
 private static final ObjectFactory DEFAULT_OBJECT_FACTORY = new DefaultObjectFactory();
 
 private static final ObjectWrapperFactory DEFAULT_OBJECT_WRAPPER_FACTORY = new DefaultObjectWrapperFactory();
 
 private static String defaultDialect = "mysql"; 
 
 private static String defaultPageSqlId = ".*4Page$"; 
 
 private static String dialect = ""; 
 
 private static String pageSqlId = ""; 
 
 public Object intercept(Invocation invocation) throws Throwable {
  StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
  metaObject metaStatementHandler = metaObject.forObject(statementHandler, DEFAULT_OBJECT_FACTORY,
    DEFAULT_OBJECT_WRAPPER_FACTORY);
  // 分离代理对象链(由于目标类可能被多个拦截器拦截，从而形成多次代理，通过下面的两次循环可以分离出最原始的的目标类)
  while (metaStatementHandler.hasGetter("h")) {
   Object object = metaStatementHandler.getValue("h");
   metaStatementHandler = metaObject.forObject(object, DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY);
  }
  // 分离最后一个代理对象的目标类
  while (metaStatementHandler.hasGetter("target")) {
   Object object = metaStatementHandler.getValue("target");
   metaStatementHandler = metaObject.forObject(object, DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY);
  }
  dialect=defaultDialect;pageSqlId=defaultPageSqlId;
  
  MappedStatement mappedStatement = (MappedStatement) metaStatementHandler.getValue("delegate.mappedStatement");
  // 只重写需要分页的sql语句。通过MappedStatement的ID匹配，默认重写以Page结尾的MappedStatement的sql
  if (mappedStatement.getId().matches(pageSqlId)) {
   BoundSql boundSql = (BoundSql) metaStatementHandler.getValue("delegate.boundSql");
   Object parameterObject = boundSql.getParameterObject();
   if (parameterObject == null) {
    throw new NullPointerException("parameterObject is null!");
   } else {
    Object obj = metaStatementHandler
      .getValue("delegate.boundSql.parameterObject.page");
    // 传入了page参数且需要开启分页时
    if(obj!=null&&obj instanceof Page &&((Page)obj).isPagination()){
     Page page = (Page) metaStatementHandler
.getValue("delegate.boundSql.parameterObject.page");
     String sql = boundSql.getSql();
     // 重写sql
     String pageSql = buildPageSql(sql, page);
     metaStatementHandler.setValue("delegate.boundSql.sql", pageSql);
     // 采用物理分页后，就不需要mybatis的内存分页了，所以重置下面的两个参数
     metaStatementHandler.setValue("delegate.rowBounds.offset", RowBounds.NO_ROW_OFFSET);
     metaStatementHandler.setValue("delegate.rowBounds.limit", RowBounds.NO_ROW_LIMIT);
     Connection connection = (Connection) invocation.getArgs()[0];
     // 重设分页参数里的总页数等
     setPageParameter(sql, connection, mappedStatement, boundSql, page);
    }
   }
  }
  // 将执行权交给下一个拦截器
  return invocation.proceed();
 }

 
 private void setPageParameter(String sql, Connection connection, MappedStatement mappedStatement,
   BoundSql boundSql, Page page) {
  // 记录总记录数
  String countSql = "select count(0) from (" + sql + ") as total";
  PreparedStatement countStmt = null;
  ResultSet rs = null;
  try {
   countStmt = connection.prepareStatement(countSql);
   BoundSql countBS = new BoundSql(mappedStatement.getConfiguration(), countSql,
     boundSql.getParameterMappings(), boundSql.getParameterObject());
   setParameters(countStmt, mappedStatement, countBS, boundSql.getParameterObject());
   rs = countStmt.executeQuery();
   int totalCount = 0;
   if (rs.next()) {
    totalCount = rs.getInt(1);
   }
   page.setTotalCount(totalCount);
   page.init(page.getCurPage(), page.getPageSize(), totalCount);

  } catch (SQLException e) {
   logger.error("Ignore this exception", e);
  } finally {
   try {
    rs.close();
   } catch (SQLException e) {
    logger.error("Ignore this exception", e);
   }
   try {
    countStmt.close();
   } catch (SQLException e) {
    logger.error("Ignore this exception", e);
   }
  }

 }

 
 private void setParameters(PreparedStatement ps, MappedStatement mappedStatement, BoundSql boundSql,
   Object parameterObject) throws SQLException {
  ParameterHandler parameterHandler = new DefaultParameterHandler(mappedStatement, parameterObject, boundSql);
  parameterHandler.setParameters(ps);
 }

 
 private String buildPageSql(String sql, Page page) {
  if (page != null) {
   StringBuilder pageSql = new StringBuilder();
   if ("mysql".equals(dialect)) {
    pageSql = buildPageSqlForMysql(sql, page);
   } else if ("oracle".equals(dialect)) {
    pageSql = buildPageSqlForOracle(sql, page);
   } else {
    return sql;
   }
   return pageSql.toString();
  } else {
   return sql;
  }
 }

 
 public StringBuilder buildPageSqlForMysql(String sql, Page page) {
  StringBuilder pageSql = new StringBuilder(100);
  String beginrow = String.valueOf((page.getCurPage() - 1) * page.getPageSize());
  pageSql.append(sql);
  pageSql.append(" limit " + beginrow + "," + page.getPageSize());
  return pageSql;
 }

 
 public StringBuilder buildPageSqlForOracle(String sql, Page page) {
  StringBuilder pageSql = new StringBuilder(100);
  String beginrow = String.valueOf((page.getCurPage() - 1) * page.getPageSize());
  String endrow = String.valueOf(page.getCurPage() * page.getPageSize());

  pageSql.append("select * from ( select temp.*, rownum row_id from ( ");
  pageSql.append(sql);
  pageSql.append(" ) temp where rownum <= ").append(endrow);
  pageSql.append(") where row_id > ").append(beginrow);
  return pageSql;
 }
 
 public Object plugin(Object target) {
  // 当目标类是StatementHandler类型时，才包装目标类，否者直接返回目标本身,减少目标被代理的次数
  if (target instanceof StatementHandler) {
   return Plugin.wrap(target, this);
  } else {
   return target;
  }
 }
 
 public void setProperties(Properties properties) {
 }

}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持考高分网。