orm映射 封装baseDao

是用orm映射封装自己封装dao层

　　思路:通过映射获得实体类的属性拼接sql语句

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import club.itstu.MyUtil.DbUtil;
import club.itstu.MyUtil.StringUtil;

/**
 * orm基础封装类
 * BaseDao.java
 * @author Mr储
 * 2016-10-20 下午9:59:30
 */

public class BaseDao<T> {
    private Class cls = null; //所操作是同类对应的Calss
    private String tableName = null; //数据库的表名
    private T t = (T) this; //当前对象
    public DbUtil db = DbUtil.getInstance();//获取数据库的连接

    public BaseDao(String tableName,Class cls){
        super();
        this.tableName = tableName;
        this.cls = cls;
    }
    /**
     * 保存对象（向数据库中增加数据）
     */
    public boolean save(){
        //通过映射获取实体类中的属性
        Field[] fields = cls.getDeclaredFields();//获取类所有属性
        //将要拼接的sql拆开
        StringBuffer sqlbf1 = new StringBuffer("insert into "+tableName+" (");//存列名
        StringBuilder sqlbf2 = new StringBuilder(" values (");
        for(Field f:fields){
            f.setAccessible(true);//私有属性设为可读
            sqlbf1.append(f.getName()+",");
            try {
                if(f.get(t)==null||StringUtil.isEmpty(f.get(t)+"")){
                    sqlbf2.append("null,");
                }else{
                    sqlbf2.append("'"+f.get(t)+"',");
                }

            } catch (IllegalArgumentException e) {
                e.printStackTrace();
                return false;
            } catch (IllegalAccessException e) {
                e.printStackTrace();
                return false;
            }
        }

        String sql1 = sqlbf1.substring(0,sqlbf1.length()-1)+")";
        String sql2 = sqlbf2.substring(0,sqlbf2.length()-1)+")";
        db.insert(sql1+sql2);//执行sql
        return true;

    }

    /**
     * 查询单个对象(一条记录)
     *
     */

    public T find(){
        //通过映射获得所有属性
        Field[] fields = cls.getDeclaredFields();
        //1=1  方便sql的拼接
        StringBuffer sqlsb = new StringBuffer("select * from "+tableName+" where 1=1");
        List<Object> params = new ArrayList<Object>();//存取属的值
        List<String> fieldNmaeList = new ArrayList<String>();//存取属性名
        //判读所有属性值是否为空
        boolean paramsFlag = true;
        for(Field f : fields){
            f.setAccessible(true);//将属性设为可读的
            fieldNmaeList.add(f.getName());//将属性名全部添加到容器中
            try {
                //判断该属性的值是否为空  +""将任何类型转换为字符串
                if(f.get(t)!=null&&StringUtil.isNotEmpty(f.get(t)+"")){
                    sqlsb.append(" and "+f.getName()+"=? ");//在sql上添加查询条件
                    params.add(f.get(t));//将该值添加到容器中
                    paramsFlag = false;//将属性值改为不全部为空
                }
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
        if(paramsFlag){//属性值权为空  返回空的对象
            return t;
        }else{
            //部位空时从数据库中取出满足改条件的记录
            List<Map<String,Object>> rstList = db.query(sqlsb.toString(),params);
            if(!rstList.isEmpty()){
                Map<String,Object> m = rstList.get(0);//取出该条数据
                //遍历将该数据 并通过属性名将该记录刚给属性赋值
                for(String fieldName : fieldNmaeList){
                    Object value = m.get(fieldName);
                    //通过映射给对象赋值
                    setValue(fieldName,value);
                }
            }
        }
        //返回该对象
        return t;
    }

    /**
     * 查询多个对象
     */
    public List<T> findAll(){
        List<T> resTList = new ArrayList<T>();//用来存储多个结果集
        Field[] fields = cls.getDeclaredFields();//获取类所有属性
        StringBuffer sfSql = new StringBuffer("select * from "+tableName+" where 1=1");
        List<Object> params = new ArrayList<Object>();//存属性值
        List<String> fieldNameList = new ArrayList<String>();//存属性名
        for(Field f:fields){
            f.setAccessible(true);//私有属性设为可读
            fieldNameList.add(f.getName());
            try {
                if(f.get(t)!=null){
                    sfSql.append(" and " +f.getName()+"=? ");
                    params.add(f.get(t));
                }
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
        List<Map<String,Object>> resList = db.query(sfSql.toString(), params);
        try {
            if(!resList.isEmpty()){
                //遍历多个结果集存入T类型的对象中
                for(Map<String,Object> map:resList){
                    T tt = (T) cls.newInstance();
                    for(String fieldName:fieldNameList){
                        Object value = map.get(fieldName);
                        setValue(fieldName,value,tt);
                    }
                    resTList.add(tt);
                }

            }
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return resTList;
    }
    /**
     * 实体对象属性赋值
     * @param name 属性名
     * @param value 属性值
     */
    private void setValue(String name,Object value){
        String setName = name.substring(0,1).toUpperCase()+name.substring(1);//将属性名的首字母大写
        String type = null;
        if(value!=null){
            type = value.getClass().getName();
            if(type.equalsIgnoreCase("java.sql.Timestamp")||type.equalsIgnoreCase("java.sql.Date")){
//                type = "java.util.Date";
                type= "java.lang.String";
                value = value+"";
            }
        }

        try {
            if(value!=null){
                Method method = cls.getDeclaredMethod("set"+setName, Class.forName(type));
                method.invoke(t, value);
            }

        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (SecurityException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }catch (Exception e) {
            e.printStackTrace();
        }
    }
    /**
     * 实体对象属性赋值
     * @param name 属性名
     * @param value 属性值
     * @param obj 要赋值的对象
     */
    private void setValue(String name,Object value,T obj){
        String setName = name.substring(0,1).toUpperCase()+name.substring(1);//将属性名的首字母大写
        String type = null;
        if(value!=null){
            type = value.getClass().getName();
            if(type.equalsIgnoreCase("java.sql.Timestamp")||type.equalsIgnoreCase("java.sql.Date")){
                //type = "java.util.Date";
                value = value+"";
                type = "java.lang.String";
            }
        }

        try {
            if(type!=null){
                Method method = cls.getDeclaredMethod("set"+setName, Class.forName(type));
                method.invoke(obj, value);
            }
        } catch (SecurityException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }catch (Exception e) {
            e.printStackTrace();
        }
    }
    /**
     * 根据id 删除对象
     */
    public boolean deleteById(){
        Method method =null;
        Integer id = null;
            try {
                method = cls.getDeclaredMethod("getId");
                id = (Integer)method.invoke(t);
                if(id==null){
                    throw new Exception("主键为空");
                }else{
                    db.delete("delete from "+tableName+" where id=?",id);
                }
            } catch (NoSuchMethodException e) {
                e.printStackTrace();
            } catch (SecurityException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        return true;
    }
    /**
     * 根据id更新
     */
    public boolean updateById(){
        //获取所有属性
        Field[] fields = cls.getDeclaredFields();
        //sql语句
        StringBuffer sqlsb = new StringBuffer("update "+tableName+" set ");

        Integer id = null;

        for(Field f : fields){
            f.setAccessible(true);//将属性设为可读的
            try {
                //是“id”这个属性进入判断
                if("id".equalsIgnoreCase(f.getName())){
                    //获得的对象为空更新失败
                    if(f.get(t)==null){
                        throw new Exception("主键id为空跟新失败");
                    }else{
                        //将该值赋给id
                        id = (Integer)f.get(t);
                    }
                }else if(f.get(t)!=null){//对象不为空进入拼接sql语句
                    sqlsb.append(f.getName()+"='"+f.get(t)+"',");
                }
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
                return false;
            } catch (IllegalAccessException e) {
                e.printStackTrace();
                return false;
            } catch (Exception e) {
                e.printStackTrace();
                return false;
            }
        }
        String sql = sqlsb.toString();
        if(sql.endsWith(",")){//该字符串逗号结束 说明属性有值 去除逗号  拼接sql
            sql = sql.substring(0,sql.length()-1)+" where id="+id;
        }else{
            try {
                throw new Exception("属性值为空，跟新失败");
            } catch (Exception e) {
                e.printStackTrace();
                return false;
            }
        }
        db.update(sql);//执行
        return true;
    }
}