mybatis下的分页支持所有的数据库

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1、大 家都知道，mybatis的自带分页方法只是逻辑分 页，如果数据量很大，内存一定会溢出，不知道为什么开源组织不在里面集成hibernate的物理分页处理方法!在不修改mybatis源代码的情况下， 应该怎么使mybatis支持物理分页呢？参考了网上的一些信息，有了下面的解决方法：以oracle为例子1.把hibernate下的dialect包全部拷贝到mybatis包的jdbc目录下，如下图所示：2.定义一个ResultSetHandler Interceptorpackage cn.machi.utils;import java.sql.Statement;import java.util

2、.Properties;import org.apache.ibatis.executor.resultset.FastResultSetHandler;import org.apache.ibatis.executor.resultset.ResultSetHandler;import org.apache.ibatis.plugin.Interceptor;import org.apache.ibatis.plugin.Intercepts;import org.apache.ibatis.plugin.Invocation;import org.apache.ibatis.plugin.

3、Plugin;import org.apache.ibatis.plugin.Signature;import org.apache.ibatis.session.RowBounds;Intercepts(Signature(type= ResultSetHandler.class, method = handleResultSets, args = Statement.class)public class DiclectResultSetHandlerInterceptor implements Interceptor public Object intercept(Invocation i

4、nvocation) throws Throwable FastResultSetHandler resultSet = (FastResultSetHandler)invocation.getTarget(); RowBounds rowBounds = (RowBounds)ReflectUtil.getFieldValue(resultSet, rowBounds); if (rowBounds.getLimit() 0 & rowBounds.getLimit() 0 & rowBounds.getLimit() RowBounds.NO_ROW_LIMIT) BoundSql bou

5、ndSql = statement.getBoundSql(); String sql = boundSql.getSql(); OracleDialect dialect = (OracleDialect)Class.forName(DIALECT) .newInstance(); sql = dialect.getLimitString(sql, rowBounds.getOffset(), rowBounds.getLimit(); ReflectUtil.setFieldValue(boundSql, sql, sql); return invocation.proceed(); pu

6、blic Object plugin(Object target) return Plugin.wrap(target, this); public void setProperties(Properties properties) 4.定义工具类ReflectUtilpackage cn.machi.utils;import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.lang.reflect.Mod

7、ifier;import org.apache.log4j.Logger;public class ReflectUtil private static Logger log = Logger.getLogger(ReflectUtil.class); private static Object operate(Object obj, String fieldName, Object fieldVal, String type) Object ret = null; try / 获得对象类型 Class classType = obj.getClass(); / 获得对象的所有属性 Field

8、 fields = classType.getDeclaredFields(); for (int i = 0; i fields.length; i+) Field field = fieldsi; if (field.getName().equals(fieldName) String firstLetter = fieldName.substring(0, 1) .toUpperCase(); / 获得和属性对应的getXXX()方法的名字 if (set.equals(type) String setMethodName = set + firstLetter + fieldName.

9、substring(1); / 获得和属性对应的getXXX()方法 Method setMethod = classType.getMethod(setMethodName, new Class field.getType(); / 调用原对象的getXXX()方法 ret = setMethod.invoke(obj, new Object fieldVal); if (get.equals(type) String getMethodName = get + firstLetter + fieldName.substring(1); / 获得和属性对应的setXXX()方法的名字 Met

10、hod getMethod = classType.getMethod(getMethodName, new Class ); ret = getMethod.invoke(obj, new Object ); return ret; catch (Exception e) log.warn(reflect error: + fieldName, e); return ret; public static Object getVal(Object obj, String fieldName) return operate(obj, fieldName, null, get); public s

11、tatic void setVal(Object obj, String fieldName, Object fieldVal) operate(obj, fieldName, fieldVal, set); private static Method getDeclaredMethod(Object object, String methodName, Class parameterTypes) for (Class superClass = object.getClass(); superClass != Object.class; superClass = superClass.getS

12、uperclass() try /superClass.getMethod(methodName, parameterTypes); return superClass.getDeclaredMethod(methodName, parameterTypes); catch (NoSuchMethodException e) /Method 不在当前类定义, 继续向上转型 return null; private static void makeAccessible(Field field) if (!Modifier.isPublic(field.getModifiers() field.s

13、etAccessible(true); private static Field getDeclaredField(Object object, String filedName) for (Class superClass = object.getClass(); superClass != Object.class; superClass = superClass.getSuperclass() try return superClass.getDeclaredField(filedName); catch (NoSuchFieldException e) /Field 不在当前类定义,

14、继续向上转型 return null; public static Object invokeMethod(Object object, String methodName, Class parameterTypes, Object parameters) throws InvocationTargetException Method method = getDeclaredMethod(object, methodName, parameterTypes); if (method = null) throw new IllegalArgumentException(Could not fin

15、d method + methodName + on target + object + ); method.setAccessible(true); try return method.invoke(object, parameters); catch (IllegalAccessException e) return null; public static void setFieldValue(Object object, String fieldName, Object value) Field field = getDeclaredField(object, fieldName); i

16、f (field = null) throw new IllegalArgumentException(Could not find field + fieldName + on target + object + ); makeAccessible(field); try field.set(object, value); catch (IllegalAccessException e) e.printStackTrace(); public static Object getFieldValue(Object object, String fieldName) Field field =

17、getDeclaredField(object, fieldName); if (field = null) throw new IllegalArgumentException(Could not find field + fieldName + on target + object + ); makeAccessible(field); Object result = null; try result = field.get(object); catch (IllegalAccessException e) e.printStackTrace(); return result; 5.更新mapper configuration文件，添加如下几条，注意plugins在整个configuration文件中的顺序6.使用方法同mybatis逻辑分页，拦截器会自动拦截执行SQL的地方，加上分页代码：getSqlSession().selectList(mapId, queryKey,new RowBounds(pageId, pageSize);