Java怎么做到代码重用

Java如何做到代码重用

首先在公共类写好数据库连接和关闭方法：

public static Connection getConnection(){
		Connection conn = null;
		try {
			Context ic = new InitialContext();
			DataSource source = (DataSource)ic.lookup("java:comp/env/jdbc/ownHome");
			conn = source.getConnection();
		} catch (NamingException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return conn;
	}
	/**
	 * 关闭连接
	 * @param conn
	 */
	public static void closeConnection(Connection conn){
		try {
			if(conn != null || (!conn.isClosed())){
				conn.close();
				conn = null;
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	/**
	 * 关闭命令
	 * @param ps
	 */
	public static void closeStatement(PreparedStatement ps){
		try {
			if(ps != null){
				ps.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	/**
	 * 关闭结果集
	 * @param rs
	 */
	public static void closeStatement(ResultSet rs){
		try {
			if(rs != null){
				rs.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
 

然后 我们把一些获取集合的公共部分提取出来：PreparedStatement 和 SQL语句

	public static PreparedStatement makeState(String sql, Object... params)
			throws Exception {		
		PreparedStatement pstmt = getConnection().prepareStatement(sql);
		for (int i = 0; i < params.length; i++) {
			pstmt.setObject(i + 1, params[i]);
		}
		return pstmt;
	}	

 这样我们就只用传入任何个数，任何类型的参数和SQL语句就行（注意：sql如果有参数必须是使用“?"标记，也可无参，只用传入SQL语句即可，这就是三点水的好处）

如：我们写了一个集合方法

public static List<Article> getArticlesBySql(String sql,Object...params){
		PreparedStatement ps = null;
		ResultSet rs = null;
		List<Article> list = new ArrayList<Article>();
	    try {
			ps = makeState(sql, params);
		} catch (Exception e1) {
			e1.printStackTrace();
		}
	    try {
			rs = ps.executeQuery();
			while (rs.next()) {
				Article article = new Article();
				article.setArticleId(rs.getInt("articleId"));
				article.setContent(rs.getString("content"));
				article.setTitle(rs.getString("title"));
				article.setType(rs.getInt("type"));
				article.setWriteDate(rs.getString("writeDate"));
				article.setWriter(rs.getString("writer"));
				list.add(article);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			GetDataBean.closeStatement(rs);
			GetDataBean.closeStatement(ps);
			GetDataBean.closeConnection(getConnection());
		}
	    return list;
		
	}

 

这个集合就可以重复使用：

/**
	 * 获取所有的标题（int)by type）
	 */
	public static List<Article> getArticles(int type){
		String sql = "select * from article where type=?";
		return GetDataBean.getArticlesBySql(sql, type);
	}
	/**
	 * 获取所有的标题（(int)by type,(String)by usrname）
	 */
	public static List<Article> getArticles(int type,String username){
		String sql = "select * from article where type=? and writer=?";
		return GetDataBean.getArticlesBySql(sql, type, username);
	}
	/**
	 * 搜索
	 * @param type
	 * @param title
	 * @param writer
	 * @return
	 */
	public static List<Article> getArticles(int type,String title,String writer){
		String sql = "select * from article where type=? and writer=? and title=? ";
		return GetDataBean.getArticlesBySql(sql, type, writer, title);
	}