refactor(Page): 重构 Page 分页对象

采用继承的方式重构 Page 分页对象，减少无用代码

1.解决重写了过时方法的问题
2.修复“因没有修改 hashNext()方法”而可能导致的 bug

Author: juzi214032

src/main/java/io/github/talelin/latticy/common/mybatis/Page.java

@@ -1,68 +1,22 @@
 package io.github.talelin.latticy.common.mybatis;
 
-import com.baomidou.mybatisplus.core.metadata.IPage;
-import com.baomidou.mybatisplus.core.metadata.OrderItem;
-import com.baomidou.mybatisplus.core.toolkit.CollectionUtils;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
-import java.util.function.Predicate;
-
 /**
- * 简单分页模型
- * mybatis-plus的默认分页实现，起始页都是1，为了与其它端保持一致，故重写了Page，起始页从 0 开始
+ * 为和其他端保持一致
+ * 重写 MyBatis-Plus 分页对象，将起始页从 1 改为 0
  *
- * @author hubin
- * @since 2018-06-09
+ * @author Juzi@TaleLin
  */
-public class Page<T> implements IPage<T> {
+public class Page<T> extends com.baomidou.mybatisplus.extension.plugins.pagination.Page<T> {
 
-    private static final long serialVersionUID = 8545996863226528798L;
-
-    /**
-     * 查询数据列表
-     */
-    private List<T> records = Collections.emptyList();
+    private static final long serialVersionUID = -2183463672525305273L;
 
     /**
-     * 总数
-     */
-    private long total = 0;
-    /**
-     * 每页显示条数，默认 10
+     * 该构造方法使得 current 总为 0
      */
-    private long size = 10;
-
-    /**
-     * 当前页
-     */
-    private long current = 0;
-
-    /**
-     * 排序字段信息
-     */
-    private List<OrderItem> orders = new ArrayList<>();
-
-    /**
-     * 自动优化 COUNT SQL
-     */
-    private boolean optimizeCountSql = true;
-    /**
-     * 是否进行 count 查询
-     */
-    private boolean isSearchCount = true;
-
     public Page() {
+        super.setCurrent(0);
     }
 
-    /**
-     * 分页构造函数
-     *
-     * @param current 当前页
-     * @param size    每页显示条数
-     */
     public Page(long current, long size) {
         this(current, size, 0);
     }
@@ -75,255 +29,29 @@ public Page(long current, long size, boolean isSearchCount) {
         this(current, size, 0, isSearchCount);
     }
 
-    public Page(long current, long size, long total, boolean isSearchCount) {
-        if (current > 0) {
-            this.current = current;
-        } else {
-            // <= 0 页，就从0页开始
-            this.current = 0;
-        }
-        this.size = size;
-        this.total = total;
-        this.isSearchCount = isSearchCount;
-    }
-
-    /**
-     * 是否存在上一页
-     *
-     * @return true / false
-     */
-    public boolean hasPrevious() {
-        return this.current > 0;
-    }
-
-    /**
-     * 是否存在下一页
-     *
-     * @return true / false
-     */
-    public boolean hasNext() {
-        return this.current < this.getPages();
-    }
-
-    @Override
-    public List<T> getRecords() {
-        return this.records;
-    }
-
-    @Override
-    public Page<T> setRecords(List<T> records) {
-        this.records = records;
-        return this;
-    }
-
-    @Override
-    public long getTotal() {
-        return this.total;
-    }
-
-    @Override
-    public Page<T> setTotal(long total) {
-        this.total = total;
-        return this;
-    }
-
-    @Override
-    public long getSize() {
-        return this.size;
-    }
-
-    @Override
-    public Page<T> setSize(long size) {
-        this.size = size;
-        return this;
-    }
-
-    @Override
-    public long getCurrent() {
-        return this.current;
-    }
-
-    @Override
-    public Page<T> setCurrent(long current) {
-        this.current = current;
-        return this;
-    }
-
-    /**
-     * 获取当前正序排列的字段集合
-     * <p>
-     * 为了兼容，将在不久后废弃
-     *
-     * @return 正序排列的字段集合
-     * @see #getOrders()
-     * @deprecated 3.1.2.2-SNAPSHOT
-     */
-    @Override
-    @Deprecated
-    public String[] ascs() {
-        return CollectionUtils.isNotEmpty(orders) ? mapOrderToArray(OrderItem::isAsc) : null;
-    }
-
-    /**
-     * 查找 order 中正序排序的字段数组
-     *
-     * @param filter 过滤器
-     * @return 返回正序排列的字段数组
-     */
-    private String[] mapOrderToArray(Predicate<OrderItem> filter) {
-        List<String> columns = new ArrayList<>(orders.size());
-        orders.forEach(i -> {
-            if (filter.test(i)) {
-                columns.add(i.getColumn());
-            }
-        });
-        return columns.toArray(new String[0]);
-    }
-
-    /**
-     * 移除符合条件的条件
-     *
-     * @param filter 条件判断
-     */
-    private void removeOrder(Predicate<OrderItem> filter) {
-        for (int i = orders.size() - 1; i >= 0; i--) {
-            if (filter.test(orders.get(i))) {
-                orders.remove(i);
-            }
-        }
-    }
-
-    /**
-     * @param items 条件
-     * @return 返回分页参数本身
-     */
-    public Page<T> addOrder(OrderItem... items) {
-        orders.addAll(Arrays.asList(items));
-        return this;
-    }
-
-    /**
-     * 设置需要进行正序排序的字段
-     * <p>
-     * Replaced:{@link #addOrder(OrderItem...)}
-     *
-     * @param ascs 字段
-     * @return 返回自身
-     * @deprecated 3.1.2.2-SNAPSHOT
-     */
-    @Deprecated
-    public Page<T> setAscs(List<String> ascs) {
-        return CollectionUtils.isNotEmpty(ascs) ? setAsc(ascs.toArray(new String[0])) : this;
-    }
-
-    /**
-     * 升序
-     * <p>
-     * Replaced:{@link #addOrder(OrderItem...)}
-     *
-     * @param ascs 多个升序字段
-     * @deprecated 3.1.2.2-SNAPSHOT
-     */
-    @Deprecated
-    public Page<T> setAsc(String... ascs) {
-        // 保证原来方法 set 的语意
-        removeOrder(OrderItem::isAsc);
-        for (String s : ascs) {
-            addOrder(OrderItem.asc(s));
-        }
-        return this;
-    }
-
     /**
-     * 获取需简要倒序排列的字段数组
-     * <p>
-     *
-     * @return 倒序排列的字段数组
-     * @see #getOrders()
-     * @deprecated 3.1.2.2-SNAPSHOT
+     * 该构造方法将小于 0 的 current 置为 0
+     * @param current 当前页
+     * @param size 每页显示条数，默认 10
+     * @param total 总数
+     * @param isSearchCount 是否进行 count 查询
      */
-    @Override
-    @Deprecated
-    public String[] descs() {
-        return mapOrderToArray(i -> !i.isAsc());
-    }
+    public Page(long current, long size, long total, boolean isSearchCount) {
+        super(current, size, total, isSearchCount);
 
-    /**
-     * Replaced:{@link #addOrder(OrderItem...)}
-     *
-     * @param descs 需要倒序排列的字段
-     * @return 自身
-     * @deprecated 3.1.2.2-SNAPSHOT
-     */
-    @Deprecated
-    public Page<T> setDescs(List<String> descs) {
-        // 保证原来方法 set 的语意
-        if (CollectionUtils.isNotEmpty(descs)) {
-            removeOrder(item -> !item.isAsc());
-            for (String s : descs) {
-                addOrder(OrderItem.desc(s));
-            }
+        if (current < 0) {
+            current = 0;
         }
-        return this;
-    }
-
-    /**
-     * 降序，这方法名不知道是谁起的
-     * <p>
-     * Replaced:{@link #addOrder(OrderItem...)}
-     *
-     * @param descs 多个降序字段
-     * @deprecated 3.1.2.2-SNAPSHOT
-     */
-    @Deprecated
-    public Page<T> setDesc(String... descs) {
-        setDescs(Arrays.asList(descs));
-        return this;
+        super.setCurrent(current);
     }
 
     @Override
-    public List<OrderItem> orders() {
-        return getOrders();
-    }
-
-    public List<OrderItem> getOrders() {
-        return orders;
-    }
-
-    public void setOrders(List<OrderItem> orders) {
-        this.orders = orders;
-    }
-
-    @Override
-    public boolean optimizeCountSql() {
-        return optimizeCountSql;
-    }
-
-    @Override
-    public boolean isSearchCount() {
-        if (total < 0) {
-            return false;
-        }
-        return isSearchCount;
-    }
-
-    public Page<T> setSearchCount(boolean isSearchCount) {
-        this.isSearchCount = isSearchCount;
-        return this;
-    }
-
-    public Page<T> setOptimizeCountSql(boolean optimizeCountSql) {
-        this.optimizeCountSql = optimizeCountSql;
-        return this;
+    public boolean hasPrevious() {
+        return super.getCurrent() > 0;
     }
 
-    /**
-     * 重写计算偏移量，将分页从第 0 开始
-     *
-     * @return 偏移量
-     */
     @Override
-    public long offset() {
-        return getCurrent() * getSize();
+    public boolean hasNext() {
+        return super.getCurrent() + 1 < this.getPages();
     }
 }