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！