package com.YU.util;
import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import com.YU.entity.Book;
public class BaseDao<T> {
  /**
   * 通用查询的basedao
   * @param sql
   * @param clz
   * @param pageBean
   * @return
   * @throws Exception
   */
  public List<T> executeQuery(String sql,Class clz,PageBean pageBean) throws Exception{
    List<T> list = new ArrayList<T>();
    Connection conn = DBAccess.getConnection();
    PreparedStatement ps = conn.prepareStatement(countSQL);
    ResultSet rs = ps.executeQuery();
    while(rs.next()) {
      //利用反射获取到对象
      T t = (T) clz.newInstance();
      //拿到clz对应所有的属性对象
      Field[] fields = clz.getDeclaredFields();
      for (Field f : fields) {
        f.setAccessible(true);
        f.set(t, rs.getObject(f.getName()));
      }
      list.add(t);
    }
    return list;
  }
}

public List<Book> find1(Book book,PageBean pageBean) throws Exception{
    List<Book> list = new ArrayList<Book>();
    Connection conn = DBAccess.getConnection();
    String sql = "select * from t_mvc_book where 1=1";
    String bname = book.getBname();
    if(StringUtils.isNotBlank(bname)) {
      sql+=" and bname like '%"+bname+"%'";
    }
    PreparedStatement ps = conn.prepareStatement(sql);
    ResultSet rs = ps.executeQuery();
    while(rs.next()) {
      Book b = new Book();
      b.setBid(rs.getInt("bid"));
      b.setBname(rs.getString("bname"));
      b.setPrice(rs.getFloat("price"));
      list.add(b);
    }
    return list;
  }

public List<Book> find2(Book book,PageBean pageBean) throws Exception{
    String sql = "select * from t_mvc_book where 1=1";
    String bname = book.getBname();
    if(StringUtils.isNotBlank(bname)) {
      sql+=" and bname like '%"+bname+"%'";
    }
    return super.executeQuery(sql, Book.class, pageBean);
  }

public List<T> executeQuery(String sql,Class clz,PageBean pageBean) throws Exception{
    List<T> list = new ArrayList<T>();
    Connection conn = null;
    PreparedStatement ps = null;
    ResultSet rs = null;
    if(pageBean!=null && pageBean.isPagination()) {
      //获取记录数
      String countSQL = getCountSQL(sql);
      conn = DBAccess.getConnection();
      ps = conn.prepareStatement(countSQL);
      rs = ps.executeQuery();
      if(rs.next()) {
        pageBean.setTotal(rs.getObject("n").toString());
      }
      //获取到SQl语句分页的数据
      String pageSQL = getPageSQL(sql,pageBean);
      conn = DBAccess.getConnection();
      ps = conn.prepareStatement(pageSQL);
      rs = ps.executeQuery();
    }else {
      conn = DBAccess.getConnection();
      ps = conn.prepareStatement(sql);
      rs = ps.executeQuery();
    }
    while(rs.next()) {
      //利用反射获取到对象
      T t = (T) clz.newInstance();
      //拿到clz对应所有的属性对象
      Field[] fields = clz.getDeclaredFields();
      for (Field f : fields) {
        f.setAccessible(true);
        f.set(t, rs.getObject(f.getName()));
      }
      list.add(t);
    }
    return list;
  }
  /**
   * 查询最后分页数据的方法
   * @param sql
   * @param pageBean
   * @return
   */
  private String getPageSQL(String sql, PageBean pageBean) {
    return sql+" limit "+pageBean.getStartIndex()+","+pageBean.getRows();
  }
  /**
   * 查询记录数的方法
   * @param sql
   * @return
   */
  private String getCountSQL(String sql) {
    return "select count(1) as n from ("+sql+") t";
  }

Book [bid=45, bname=圣墟第45章, price=45.0]
Book [bid=46, bname=圣墟第46章, price=46.0]
Book [bid=47, bname=圣墟第47章, price=47.0]
Book [bid=49, bname=圣墟第49章, price=49.0]
Book [bid=50, bname=圣墟第50章, price=50.0]
Book [bid=51, bname=圣墟第51章, price=51.0]
Book [bid=52, bname=圣墟第52章, price=52.0]
Book [bid=53, bname=圣墟第53章, price=53.0]
Book [bid=54, bname=圣墟第54章, price=54.0]
Book [bid=55, bname=圣墟第55章, price=55.0]
PageBean [page=3, rows=10, total=85, pagination=true]