基于JDBC封裝的BaseDao(實(shí)例代碼)

更新時(shí)間：2016年07月15日 09:32:56 投稿：jingxian

下面小編就為大家?guī)?lái)一篇基于JDBC封裝的BaseDao(實(shí)例代碼)。小編覺(jué)得挺不錯(cuò)的，現(xiàn)在就分享給大家，也給大家做個(gè)參考。一起跟隨小編過(guò)來(lái)看看吧

最近閑暇時(shí)萌發(fā)寫(xiě)一寫(xiě)dao的封裝的例子，就將以前寫(xiě)的整理一下。

public class BaseDao<T> {

	Connection conn;
	PreparedStatement st;
	ResultSet rs;
	
	JdbcUtil jdbcUtil = new JdbcUtil();
	
	int result = 0;
	
	private Class<T> persistentClass;
	
	@SuppressWarnings("unchecked")
	public BaseDaoUtil(){		
		conn = jdbcUtil.getConnection();
		ParameterizedType type = (ParameterizedType) getClass().getGenericSuperclass();
		persistentClass = (Class<T>) type.getActualTypeArguments()[0];		
	}
	
	
  /**
   * 保存
    * @param entity
   * @return
   */
	public int save(T entity) throws Exception{
		
		String sql = "INSERT INTO "+ entity.getClass().getSimpleName().toLowerCase() +" (";
		
		List<Method> list = this.matchPojoMethods(entity,"get");
		
		Iterator<Method> iter = list.iterator();
			
		Object obj[] = new Object[list.size()];
		int i = 0;
		//拼接字段順序 insert into table name(id,name,email,
         while(iter.hasNext()) {
            Method method = iter.next();
            sql += method.getName().substring(3).toLowerCase() + ","; 
            if (method.getReturnType().getSimpleName().indexOf("Date") !=-1) {
				SimpleDateFormat sbf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
				obj[i] = sbf.format(method.invoke(entity, new Object[]{}));
		   }else {
				obj[i] = method.invoke(entity, new Object[]{});
		   }     
      i++;
    }
    
    //去掉最后一個(gè),符號(hào)insert insert into table name(id,name,email) values(
    sql = sql.substring(0, sql.lastIndexOf(",")) + ") values(";
    
    //拼裝預(yù)編譯SQL語(yǔ)句insert insert into table name(id,name,email) values(?,?,?,
    for(int j = 0; j < list.size(); j++) {
    	sql += "?,"; 
    }

    //去掉SQL語(yǔ)句最后一個(gè),符號(hào)insert insert into table name(id,name,email) values(?,?,?);
    sql = sql.substring(0, sql.lastIndexOf(",")) + ")";
    
    //到此SQL語(yǔ)句拼接完成,打印SQL語(yǔ)句
    System.out.println(sql);
    
    try {
    	st = conn.prepareStatement(sql);
    	for (int j = 0; j < obj.length; j++) {
				st.setObject(j+1, obj[j]);
			}
			result = st.executeUpdate();
		} catch (SQLException e) {
			e.printStackTrace();
		}
    
		jdbcUtil.getClose(rs, st, conn);
		
		return result;	
	}
	
	/**
	 * 刪除
	 * @param object
	 * @return
	 * @throws SQLException
	 */
	public int deleteId(Object object) throws Exception{
		
		String sql = "delete from "+ persistentClass.getSimpleName().toLowerCase() +" where ";
		
		//通過(guò)子類的構(gòu)造函數(shù),獲得參數(shù)化類型的具體類型.比如BaseDAO<T>也就是獲得T的具體類型
    T entity = persistentClass.newInstance();
    
    //存放Pojo(或被操作表)主鍵的方法對(duì)象
    Method idMethod = null;
    
    List<Method> list = this.matchPojoMethods(entity, "set");
    Iterator<Method> iter = list.iterator();
    
    //過(guò)濾取得Method對(duì)象
    while(iter.hasNext()) {
      Method tempMethod = iter.next();
      if(tempMethod.getName().indexOf("Id") != -1 && tempMethod.getName().substring(3).length() == 2) {
        idMethod = tempMethod;
      } else if((entity.getClass().getSimpleName() + "Id").equalsIgnoreCase(tempMethod.getName().substring(3))){
        idMethod = tempMethod;
      }
    }
    //第一個(gè)字母轉(zhuǎn)為小寫(xiě)
    sql += idMethod.getName().substring(3,4).toLowerCase()+idMethod.getName().substring(4) + " = ?";
    	
		System.out.println(sql);
		
		st = conn.prepareStatement(sql);
		
		//判斷id的類型
    if(object instanceof Integer) {
      st.setInt(1, (Integer)object);
    } else if(object instanceof String){
      st.setString(1, (String)object);
    }
		
		result = st.executeUpdate();
		
		jdbcUtil.getClose(rs, st, conn);
		
		return result;	
	}
	
	/**
	 * 修改
	 * @param entity
	 * @return
	 * @throws Exception
	 */
	public int update(T entity) throws Exception{
		
		String sql = "update "+ entity.getClass().getSimpleName().toLowerCase() +" set ";
		
		List<Method> list = this.matchPojoMethods(entity, "get");
		
		//裝載參數(shù)
		Object obj[] = new Object[list.size()];
		int i = 0;
		
		//臨時(shí)Method對(duì)象,負(fù)責(zé)迭代時(shí)裝method對(duì)象.
    Method tempMethod = null;
    
    //由于修改時(shí)不需要修改ID,所以按順序加參數(shù)則應(yīng)該把Id移到最后.
    Method idMethod = null;
    Iterator<Method> iter = list.iterator();
    while(iter.hasNext()) {
      tempMethod = iter.next();
 
      //如果方法名中帶有ID字符串并且長(zhǎng)度為2,則視為ID.
      if(tempMethod.getName().lastIndexOf("Id") != -1 && tempMethod.getName().substring(3).length() == 2) {
      	obj[list.size()-1] = tempMethod.invoke(entity, new Object[]{});
        //把ID字段的對(duì)象存放到一個(gè)變量中,然后在集合中刪掉.
        idMethod = tempMethod;
        iter.remove();
      //如果方法名去掉set/get字符串以后與pojo + "id"想符合(大小寫(xiě)不敏感),則視為ID
      } else if((entity.getClass().getSimpleName() + "Id").equalsIgnoreCase(tempMethod.getName().substring(3))) {
      	obj[list.size()-1] = tempMethod.invoke(entity, new Object[]{});
      	idMethod = tempMethod;
        iter.remove();        
      }
    }
		
    //把迭代指針移到第一位
    iter = list.iterator();
    while(iter.hasNext()) {
      tempMethod = iter.next();
      sql += tempMethod.getName().substring(3).toLowerCase() + "= ?,";
      obj[i] = tempMethod.invoke(entity, new Object[]{});
      i++;
    }
    
    //去掉最后一個(gè),符號(hào)
    sql = sql.substring(0,sql.lastIndexOf(","));
    
    //添加條件
    sql += " where " + idMethod.getName().substring(3).toLowerCase() + " = ?";
    
    //SQL拼接完成,打印SQL語(yǔ)句
    System.out.println(sql);
		
    st = conn.prepareStatement(sql);
    
    for (int j = 0; j < obj.length; j++) {
			st.setObject(j+1, obj[j]);
		}
    
    result = st.executeUpdate();

    jdbcUtil.getClose(rs, st, conn);
    
		return result;

	}
	
	
	public T findById(Object object) throws Exception{
		
		String sql = "select * from "+ persistentClass.getSimpleName().toLowerCase() +" where ";
		
		//通過(guò)子類的構(gòu)造函數(shù),獲得參數(shù)化類型的具體類型.比如BaseDAO<T>也就是獲得T的具體類型
    T entity = persistentClass.newInstance();
    
    //存放Pojo(或被操作表)主鍵的方法對(duì)象
    Method idMethod = null;
    
    List<Method> list = this.matchPojoMethods(entity, "set");
    Iterator<Method> iter = list.iterator();
    
    //過(guò)濾取得Method對(duì)象
    while(iter.hasNext()) {
      Method tempMethod = iter.next();
      if(tempMethod.getName().indexOf("Id") != -1 && tempMethod.getName().substring(3).length() == 2) {
        idMethod = tempMethod;
      } else if((entity.getClass().getSimpleName() + "Id").equalsIgnoreCase(tempMethod.getName().substring(3))){
        idMethod = tempMethod;
      }
    }
    //第一個(gè)字母轉(zhuǎn)為小寫(xiě)
    sql += idMethod.getName().substring(3,4).toLowerCase()+idMethod.getName().substring(4) + " = ?";
    	
		System.out.println(sql);
		
		st = conn.prepareStatement(sql);
		
		//判斷id的類型
    if(object instanceof Integer) {
      st.setInt(1, (Integer)object);
    } else if(object instanceof String){
      st.setString(1, (String)object);
    }
		
    rs = st.executeQuery();
        
    //把指針指向迭代器第一行
    iter = list.iterator();
    
    //封裝
    while(rs.next()) {
      while(iter.hasNext()) {
        Method method = iter.next();
        if(method.getParameterTypes()[0].getSimpleName().indexOf("String") != -1) {
          //由于list集合中,method對(duì)象取出的方法順序與數(shù)據(jù)庫(kù)字段順序不一致(比如:list的第一個(gè)方法是setDate,而數(shù)據(jù)庫(kù)按順序取的是"123"值)
          //所以數(shù)據(jù)庫(kù)字段采用名字對(duì)應(yīng)的方式取.
          this.setString(method, entity, rs.getString(method.getName().substring(3).toLowerCase()));
        } else if(method.getParameterTypes()[0].getSimpleName().indexOf("Date") != -1){
          this.setDate(method, entity, rs.getDate(method.getName().substring(3).toLowerCase()));
        }else {
          this.setInt(method, entity, rs.getInt(method.getName().substring(3).toLowerCase()));
        }  
      }
    }
		
    jdbcUtil.getClose(rs, st, conn);
    
		return entity;
		
	}
	
	
	
	
	
	/**
   * 過(guò)濾當(dāng)前Pojo類所有帶傳入字符串的Method對(duì)象,返回List集合.
   */
  private List<Method> matchPojoMethods(T entity,String methodName) {
    //獲得當(dāng)前Pojo所有方法對(duì)象
    Method[] methods = entity.getClass().getDeclaredMethods();
    
    //List容器存放所有帶get字符串的Method對(duì)象
    List<Method> list = new ArrayList<Method>();
    
    //過(guò)濾當(dāng)前Pojo類所有帶get字符串的Method對(duì)象,存入List容器
    for(int index = 0; index < methods.length; index++) {
      if(methods[index].getName().indexOf(methodName) != -1) {
        list.add(methods[index]);
      }
    }    
    return list;
  }
  

  /**
   * 參數(shù)類型為String時(shí),為entity字段設(shè)置參數(shù),對(duì)應(yīng)set
   */
  public String setString(Method method, T entity, String arg) throws Exception{
    return (String)method.invoke(entity, new Object[]{arg});
  }
  
  
  /**
   * 參數(shù)類型為Date時(shí),為entity字段設(shè)置參數(shù),對(duì)應(yīng)set
   */
  public Date setDate(Method method, T entity, Date arg) throws Exception{
    return (Date)method.invoke(entity, new Object[]{arg});
  }
	
	
  /**
   * 參數(shù)類型為Integer或int時(shí),為entity字段設(shè)置參數(shù),對(duì)應(yīng)set
   */
  public Integer setInt(Method method, T entity, Integer arg) throws Exception{
    return (Integer)method.invoke(entity, new Object[]{arg});
  }
 	
}

以上這篇基于JDBC封裝的BaseDao(實(shí)例代碼)就是小編分享給大家的全部?jī)?nèi)容了，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

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