选课系统综合作业 Java学习资料

package com.xyzboom.utils; import com.xyzboom.database.entity.Entity; import com.xyzboom.database.entity.EntityColumnEnum; import com.xyzboom.database.entity.exception.EntityColumnException; import com.xyzboom.database.entity.exception.NotEntityClassException; import com.xyzboom.database.utils.SQLLimit; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.List; public class Page<T> { private Enum<?> entityColumnNull; private Class<?> entityColumnClass; private Enum<?> orderBy = null; private boolean descend = false; public Enum<?> getOrderBy() { return orderBy; } public boolean isDescend() { return descend; } public void setOrderBy(String orderBy) { try { Method fromStringMethod = entityColumnClass. getDeclaredMethod(EntityColumnEnum.FROM_STRING_METHOD_NAME, String.class); this.orderBy = (Enum<?>) fromStringMethod.invoke(null, orderBy); } catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException e) { this.orderBy = entityColumnNull; } } public void setDescend(String descend) { try { this.descend = Boolean.parseBoolean(descend); } catch (Exception e) { this.descend = false; } } @SuppressWarnings("unchecked") public static <T> Page<T> cast(Page<?> page) { return (Page<T>) page; } public interface SimplePageDelegate<T1> { List<T1> getSimplePage(Enum<?> orderBy, boolean descend, SQLLimit limit); } public interface TotalSizeDelegate { Integer getTotalSize(); } public SimplePageDelegate<T> getSimplePageDelegate() { return simplePageDelegate; } public void setSimplePageDelegate(SimplePageDelegate<T> simplePageDelegate) { this.simplePageDelegate = simplePageDelegate; } private SimplePageDelegate<T> simplePageDelegate; public TotalSizeDelegate getTotalSizeDelegate() { return totalSizeDelegate; } public void setTotalSizeDelegate(TotalSizeDelegate totalSizeDelegate) { this.totalSizeDelegate = totalSizeDelegate; } private TotalSizeDelegate totalSizeDelegate; /** * 显示的页码数量<br/> * 例如:<br/> * &lt;前一页 1 2 ... 5 6 7 ... 12 13 后一页&gt;<br/> * 以上写法共9页，省略号也算2页 */ private int showPageNum = 9; public Page(SimplePageDelegate<T> simplePageDelegate, TotalSizeDelegate totalSizeDelegate, Class<?> entityClass) throws NotEntityClassException, EntityColumnException { if (entityClass.getAnnotation(Entity.class) == null) { throw new NotEntityClassException("Class " + entityClass + " is not an Entity Class"); } Method method; try { method = entityClass.getDeclaredMethod(Entity.GET_COLUMN_ENUM_METHOD_NAME); } catch (NoSuchMethodException e) { throw new NotEntityClassException( "Class " + entityClass + " has @Entity but does not have " + Entity.GET_COLUMN_ENUM_METHOD_NAME + " method"); } try { Object o = method.invoke(null); if (o != null) { entityColumnClass = (Class<?>) o; if (entityColumnClass.getAnnotation(EntityColumnEnum.class) == null) { throw new EntityColumnException("Not a column class"); } Method getColumnNullMethod; getColumnNullMethod = entityColumnClass. getDeclaredMethod(EntityColumnEnum.GET_COLUMN_NULL_METHOD_NAME); Object o1 = getColumnNullMethod.invoke(null); this.entityColumnNull = (Enum<?>) o1; } } catch (IllegalAccessException | InvocationTargetException | ClassCastException e) { throw new EntityColumnException("Fail to get entity's column class"); } catch (NoSuchMethodException e) { throw new EntityColumnException( "Class " + entityColumnClass + " has @Entity but does not have " + EntityColumnEnum.GET_COLUMN_NULL_METHOD_NAME + " method"); } this.simplePageDelegate = simplePageDelegate; this.totalSizeDelegate = totalSizeDelegate; } public int getShowPageNum() { return showPageNum; } public void setShowPageNum(int showPageNum) { this.showPageNum = showPageNum; } /** * 当前页码 */ private int pageNo = 1; /** * 分页大小，即{@link Page#getList}的最大大小 */ private int pageSize = 10; public int getPageSize() { return pageSize; } public void setPageSize(int pageSize) { this.pageSize = pageSize; } public static class PageSizeOutOfBoundsException extends IndexOutOfBoundsException { public PageSizeOutOfBoundsException() { } public PageSizeOutOfBoundsException(String s) { super(s); } } public int getPageNo() { return pageNo; } public void setPageNo(int pageNo) { int totalSize = getTotalElementSize(); int maxPageNo = (int) Math.ceil(totalSize * 1.0 / pageSize); if (pageNo > maxPageNo) { throw new PageSizeOutOfBoundsException(); } if (pageNo <= 0) { throw new PageSizeOutOfBoundsException(); } this.pageNo = pageNo; } /** * 获取当前页面内容 * * @return null 如果发生错误 */ public List<T> getList(Enum<?> oderBy, boolean descend) { return simplePageDelegate.getSimplePage(oderBy, descend, new SQLLimit(pageNo - 1, pageSize)); } public List<T> getList() { if (orderBy == null) { orderBy = entityColumnNull; } return getList(orderBy, descend); } /** * 总{@link T}的数量<br/> * * @return null 如果发生错误 */ public Integer getTotalElementSize() { return totalSizeDelegate.getTotalSize(); } public int getPrevPage() { if (pageNo > 1) { return pageNo - 1; } return -1; } public int getTotalPageSize() { int totalSize = getTotalElementSize(); return (int) Math.ceil(totalSize * 1.0 / pageSize); } public int getNextPage() { if (pageNo < getTotalPageSize()) { return pageNo + 1; } return -1; } }