简单泛型DAO的实现

一个简单的泛型DAO的实现
package dao;


import java.util.List;

public interface SelectSQL {


    //1.查询所有
    public <T>List<T> getUser(T t);

    //2.根据姓名查询年龄
    public <T> int getAge(String name,T t);

    //3.查询前n条信息
    public <T> List<T> getUser(int n,T t);

    //4.查询有多少条记录
    public <T> int getNum(T t);

    //5.对年龄进行升序排序
    public <T> List<T> getAgeASC(T t);

    //6.对姓名进行升序排序
    public <T> List<T> getNameASC(T t);

    //7.根据性别记行分组
    public <T> List<T> getUserGroup(T t);

    //8.查询年龄在 x ~ y 之间的人
    public <T> List<T> getAgeXY(int x,int y,T t);

    //9.查询年龄在 x ~ y 之间的 男/女 
    public <T> List<T> getAgeXY(int x,int y,String sex,T t);

    //10.查询年龄在 x ~ y 之间的 男/女 并按降序排序
    public <T> List<T> getAgeXYDesc(int x,int y,String sex,T t);

    //11.查询当页的对象
    public <T> List<T> findByPage(int page,T t);

    //12.获取总的记录数
    public <T> int getCount(T t);

}
这是随意的12个查询方法；
package dao.impl;


import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import dao.SelectSQL;
import util.ConnectionManager;


public class SelectSQLImpl implements SelectSQL{


    Connection conn = ConnectionManager.getConnection();
    @Override
    public <T> List<T> getUser(T t) {   
        @SuppressWarnings("rawtypes")
        Class clazz1 = t.getClass();
        List<T> list = new ArrayList<T>();
        String clazz = clazz1.getSimpleName(); //得到类的简单名称
        String sql = "select * from " + clazz;
        Statement st = null;
        ResultSet rs = null;
        try {
            st = conn.createStatement();
            rs = st.executeQuery(sql);
            System.out.println(sql);
            while(rs.next()){
                @SuppressWarnings("unchecked")
                T t1 = (T) clazz1.newInstance(); //根据反射创建对象
                Field[] fs = clazz1.getDeclaredFields(); //得到类中所有属性的集合
                for(int i=0; i<fs.length; i++){ //变量属性集合
                Field f = fs[i];
                f.setAccessible(true);  //设置为true时，在反射是可以访问该变量
                String type1 = f.getType().toString(); //得到此属性的类型
                if(type1.endsWith("String")){ //如果是String类型
                    f.set(t1, rs.getString(i+1));   //给属性设置
                }else if(type1.endsWith("int")){
                    f.set(t1, rs.getInt(i+1));
                }else{
                    f.set(t1, rs.getObject(i+1));
                }

                }
                list.add(t1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        }
        return list;
    }
    @Override
    public <T> int getAge(String name, T t) {
        @SuppressWarnings("rawtypes")
        Class clazz = t.getClass();
        String clazzName = clazz.getSimpleName();
        String sql = "select age from " + clazzName + " where name = '" + name + "'";
        Statement st = null;
        ResultSet rs = null;
        int age = 0;
        try {
            st = conn.createStatement();
            rs = st.executeQuery(sql);
            while(rs.next()){
                age = rs.getInt(1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return age;
    }
    @Override
    public <T> List<T> getUser(int n, T t) {
        List<T> list = new ArrayList<T>();
        @SuppressWarnings("rawtypes")
        Class clazz = t.getClass();
        String clazzName = clazz.getSimpleName();
        String sql = "select * from " + clazzName + " where id = " + n ;
        Statement st = null;
        ResultSet rs = null;

        try {
            st = conn.createStatement();
            rs = st.executeQuery(sql);
            System.out.println("00 " + sql);
            while(rs.next()){
                @SuppressWarnings("unchecked")
                T t1 = (T) clazz.newInstance();
                Field[] fs = clazz.getDeclaredFields();
                for(int i=0; i< fs.length; i++){
                    Field f = fs[i];
                    f.setAccessible(true);
                    String type = f.getType().toString();
                    if(type.endsWith("String")){
                        f.set(t1, rs.getString(i+1));
                    }else if(type.endsWith("int")){
                        f.set(t1, rs.getInt(i+1));
                    }else{
                        f.set(t1,rs.getObject(i+1));
                    }
                }
                list.add(t1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return list;
    }
    @Override
    public <T> int getNum(T t) {
        @SuppressWarnings("rawtypes")
        Class clazz = t.getClass();
        String simpleName = clazz.getSimpleName();
        String sql = "select count(*) from " + simpleName;
        Statement st = null;
        ResultSet rs = null;
        int i = 0;
        try {
            st = conn.createStatement();
            rs = st.executeQuery(sql);
            if(rs.next()){
                i = rs.getInt(1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return i;
    }
    @Override
    public <T> List<T> getAgeASC(T t) {
        List<T> list = new ArrayList<T>();
        Class clazz = t.getClass();
        String SimpleName = clazz.getSimpleName();
        String sql = "select age from " + SimpleName + " order by age ";
        Statement st = null;
        ResultSet rs = null;

        try {
            st = conn.createStatement();
            rs = st.executeQuery(sql);

            while(rs.next()){
                T t1 = (T) clazz.newInstance();
                Field[] fs = clazz.getDeclaredFields();
                for(int i=0; i<fs.length;i++){
                    Field f = fs[i];
                    f.setAccessible(true);
                    String type = f.getType().toString();
                    if(type.endsWith("String")){
                        f.set(t1, rs.getString(i+1));
                    }else if(type.endsWith("int")){
                        f.set(t1,rs.getInt(i+1));
                    }else{
                        f.set(t1,rs.getObject(i+1));
                    }
                }
                list.add(t1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return list;
    }
    @Override
    public <T> List<T> getNameASC(T t) {
        List<T> list = new ArrayList<T>();
        Class clazz = t.getClass();
        String SimpleName = clazz.getSimpleName();
        String sql = "select * from " + SimpleName + " order by name";
        Statement st = null;
        ResultSet rs = null;

        try {
            st = conn.createStatement();
            rs = st.executeQuery(sql);

            while(rs.next()){
                T t1 = (T) clazz.newInstance();
                Field[] fs = clazz.getDeclaredFields();
                for(int i=0; i<fs.length;i++){
                    Field f = fs[i];
                    f.setAccessible(true);
                    String type = f.getType().toString();
                    if(type.endsWith("String")){
                        f.set(t1, rs.getString(i+1));
                    }else if(type.endsWith("int")){
                        f.set(t1,rs.getInt(i+1));
                    }else{
                        f.set(t1,rs.getObject(i+1));
                    }
                }
                list.add(t1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return list;
    }
    @Override
    public <T> List<T> getUserGroup(T t) {
        List<T> list = new ArrayList<T>();
        Class clazz = t.getClass();
        String SimpleName = clazz.getSimpleName();
        String sql = "select * from " + SimpleName + " group by sex";
        Statement st = null;
        ResultSet rs = null;

        try {
            st = conn.createStatement();
            rs = st.executeQuery(sql);

            while(rs.next()){
                T t1 = (T) clazz.newInstance();
                Field[] fs = clazz.getDeclaredFields();
                for(int i=0; i<fs.length;i++){
                    Field f = fs[i];
                    f.setAccessible(true);
                    String type = f.getType().toString();
                    if(type.endsWith("String")){
                        f.set(t1, rs.getString(i+1));
                    }else if(type.endsWith("int")){
                        f.set(t1,rs.getInt(i+1));
                    }else{
                        f.set(t1,rs.getObject(i+1));
                    }
                }
                list.add(t1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return list;
    }
    @Override
    public <T> List<T> getAgeXY(int x, int y, T t) {
        List<T> list = new ArrayList<T>();
        Class clazz = t.getClass();
        String SimpleName = clazz.getSimpleName();
        String sql = "select * from " + SimpleName + " where age between " + x +
                " and " + y;
        Statement st = null;
        ResultSet rs = null;

        try {
            st = conn.createStatement();
            rs = st.executeQuery(sql);

            while(rs.next()){
                T t1 = (T) clazz.newInstance();
                Field[] fs = clazz.getDeclaredFields();
                for(int i=0; i<fs.length;i++){
                    Field f = fs[i];
                    f.setAccessible(true);
                    String type = f.getType().toString();
                    if(type.endsWith("String")){
                        f.set(t1, rs.getString(i+1));
                    }else if(type.endsWith("int")){
                        f.set(t1,rs.getInt(i+1));
                    }else{
                        f.set(t1,rs.getObject(i+1));
                    }
                }
                list.add(t1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return list;
    }
    @Override
    public <T> List<T> getAgeXY(int x, int y, String sex, T t) {
        List<T> list = new ArrayList<T>();
        Class clazz = t.getClass();
        String SimpleName = clazz.getSimpleName();
        String sql = "select * from " + SimpleName + " where sex = '" +sex + "' and age "
                + "between 10 and 12" ;
        Statement st = null;
        ResultSet rs = null;

        try {
            System.out.println(sql);
            st = conn.createStatement();
            rs = st.executeQuery(sql);

            while(rs.next()){

                @SuppressWarnings("unchecked")
                T t1 = (T) clazz.newInstance();
                Field[] fs = clazz.getDeclaredFields();
                for(int i=0; i<fs.length;i++){
                    System.out.println(rs.getObject(i+1));
                    Field f = fs[i];
                    f.setAccessible(true);
                    String type = f.getType().toString();
                    if(type.endsWith("String")){
                        f.set(t1, rs.getString(i+1));
                    }else if(type.endsWith("int")){
                        f.set(t1,rs.getInt(i+1));
                    }else{
                        f.set(t1,rs.getObject(i+1));
                    }
                }
                list.add(t1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return list;
    }
    @Override
    public <T> List<T> getAgeXYDesc(int x, int y, String sex, T t) {
        List<T> list = new ArrayList<T>();
        Class clazz = t.getClass();
        String SimpleName = clazz.getSimpleName();
        String sql = "select * from " + SimpleName + " where sex = '" +sex + "' and age "
                + "between 10 and 12 order by desc" ;
        Statement st = null;
        ResultSet rs = null;

        try {
            System.out.println(sql);
            st = conn.createStatement();
            rs = st.executeQuery(sql);

            while(rs.next()){

                @SuppressWarnings("unchecked")
                T t1 = (T) clazz.newInstance();
                Field[] fs = clazz.getDeclaredFields();
                for(int i=0; i<fs.length;i++){
                    System.out.println(rs.getObject(i+1));
                    Field f = fs[i];
                    f.setAccessible(true);
                    String type = f.getType().toString();
                    if(type.endsWith("String")){
                        f.set(t1, rs.getString(i+1));
                    }else if(type.endsWith("int")){
                        f.set(t1,rs.getInt(i+1));
                    }else{
                        f.set(t1,rs.getObject(i+1));
                    }
                }
                list.add(t1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return list;
    }
    @Override
    public <T> List<T> findByPage(int page, T t) {
        @SuppressWarnings("rawtypes")
        Class clazz1 = t.getClass();
        int begin = (page-1)*5;
        List<T> list = new ArrayList<T>();
        String clazz = clazz1.getSimpleName();
        String sql = "select * from " + clazz + " limit " + begin + ",5";
        Statement st = null;
        ResultSet rs = null;
        try {
            st = conn.createStatement();
            rs = st.executeQuery(sql);
            System.out.println(sql);
            while(rs.next()){
                @SuppressWarnings("unchecked")
                T t1 = (T) clazz1.newInstance();
                Field[] fs = clazz1.getDeclaredFields(); //得到类中所有属性的集合
                for(int i=0; i<fs.length; i++){
                Field f = fs[i];
                f.setAccessible(true);
                String type1 = f.getType().toString(); //得到此属性的类型
                if(type1.endsWith("String")){
                    f.set(t1, rs.getString(i+1));   //给属性设置
                }else if(type1.endsWith("int")){
                    f.set(t1, rs.getInt(i+1));
                }else{
                    f.set(t1, rs.getObject(i+1));
                }

                }
                list.add(t1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        }
        return list;
    }
    @Override
    public <T> int getCount(T t) {
        @SuppressWarnings("rawtypes")
        Class clazz = t.getClass();
        String simpleName = clazz.getSimpleName();
        String sql = "select count(*) from " + simpleName;
        Statement st = null;
        ResultSet rs = null;
        int i = 0;
        try {
            st = conn.createStatement();
            rs = st.executeQuery(sql);
            if(rs.next()){
                i = rs.getInt(1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return i;
    }


}

这是我结合网上的一些资料自己编写的，可能会有很多不足欢迎大家指出！