古诗MySQL数据库DAO模式实现

整体规则



step1

DBHelper工具类，一般不用实例化，因此可以采用Singleton或者是将构造方法私有化。

/**
* Created by chuiyuan on 2/17/16.
* 工具类，一般不要实例化，此时可以采用单例设计模式，或者将构造方法私有化
*/
public class DBHelper {
public static String url ;
public static String username ;
public static String password ;
public static String driver ;
//prrty file
private static ResourceBundle rb =
ResourceBundle.getBundle("db-config");

//private Connection conn = null ;

private DBHelper(){

}

/**
* 为避免重复代码，使用静态代码块：只会在类加载的时候执行一次。
*/
static {
try{
url = rb.getString("jdbc.url");
username = rb.getString("jdbc.username");
password = rb.getString("jdbc.password");
driver = rb.getString("jdbc.driver");

Class.forName(driver);
}catch (Exception e ){
e.printStackTrace();
}
}
//get a connection with mysql
public static Connection getConnection(){
Connection conn = null ;
try {
conn = DriverManager.getConnection(url,username,password);
}catch (SQLException e ){
e.printStackTrace();
}
return  conn ;
}

/**
* close
* @param rs
* @param stmt
* @param conn
*/
public static void close(ResultSet rs , Statement stmt ,Connection conn){
try {
if (rs!= null) rs.close();
if (stmt!= null) stmt.close();
if (conn!= null) conn.close();
}catch (SQLException e ){
e.printStackTrace();
}
}
}

Step2

DAO接口。

/**
* Created by chuiyuan on 2/17/16.
* interface for CRUD of Poem
*/
public interface PoemDao {
public void add (Poem poem) throws SQLException;

public void update (Poem poem) throws SQLException;

public void delete(int id) throws SQLException;

public Poem findById(int id) throws SQLException ;

public List<Poem> findAll() throws SQLException ;
}

Step3

PoemDaoImpl实现step2中的接口。

/**
* Created by chuiyuan on 2/17/16.
*/
public class PoemDaoImpl implements PoemDao {

public void add(Poem poem) throws SQLException {
Connection conn = null ;
PreparedStatement ps = null ;
String sql = "insert into poemtable" +
"(dynasty, category, title, author, content, href, translation)"+
" values (?, ?, ?, ?, ?, ?, ?)";
try {
conn = DBHelper.getConnection() ;
ps = conn.prepareStatement(sql);
ps.setString(1,poem.getDynasty());
ps.setString(2,poem.getCategory());
ps.setString(3,poem.getTitle());
ps.setString(4,poem.getAuthor());
ps.setString(5,poem.getContent());
ps.setString(6,poem.getHref());
ps.setString(7,poem.getTranslation());
ps.executeUpdate();
}catch (SQLException e){
e.printStackTrace();
throw new SQLException("add poem failed");
}finally {
DBHelper.close(null, ps,conn);
}
}

public void update(Poem poem) throws SQLException {
Connection conn = null;
PreparedStatement ps = null;
String sql = "update poemtable set dynasty=?, category=?, title=?," +
" author=?, content=?, href=? ,translation=? where id=?";
try {
conn = DBHelper.getConnection();
ps = conn.prepareStatement(sql);
ps.setString(1,poem.getDynasty());
ps.setString(2,poem.getCategory());
ps.setString(3,poem.getTitle());
ps.setString(4,poem.getAuthor());
ps.setString(5,poem.getContent());
ps.setString(6,poem.getHref());
ps.setString(7,poem.getTranslation());
ps.executeUpdate();
}catch (SQLException e){
e.printStackTrace();
throw new SQLException("update poem failed");
}finally {
DBHelper.close(null,ps,conn);
}
}

public void delete(int id) throws SQLException {
Connection conn = null;
PreparedStatement ps = null;
String sql = "delete from poemtable where id=?";
try {
conn = DBHelper.getConnection();
ps = conn.prepareStatement(sql);
ps.setInt(1,id);
ps.executeUpdate();
}catch (SQLException e){
e.printStackTrace();
throw new SQLException("delete poem failed");
}finally {
DBHelper.close(null,ps, conn);
}
}

public Poem findById(int id) throws SQLException {
Connection conn = null ;
PreparedStatement ps = null;
ResultSet rs = null;
Poem poem = null;
String sql = "select dynasty,catetogry,title,author,content," +
"href from poemtable where id=?";
try {
conn = DBHelper.getConnection();
ps = conn.prepareStatement(sql);
ps.setInt(1, id);
rs = ps.executeQuery();
if (rs.next()){
poem = new Poem() ;
poem.setDynasty(rs.getString(1));
poem.setCategory(rs.getString(2));
poem.setTitle(rs.getString(3));
poem.setAuthor(rs.getString(4));
poem.setContent(rs.getString(5));
poem.setHref(rs.getString(6));
}
}catch (SQLException e){
e.printStackTrace();
throw new SQLException("find by id failed");
}finally {
DBHelper.close(rs,ps, conn);
}
return poem;
}

public List<Poem> findAll() throws SQLException {
Connection conn = null ;
PreparedStatement ps = null ;
ResultSet rs = null ;

Poem poem = null ;
List<Poem> poemList = new ArrayList<Poem>();

String sql = "select dynasty,catetogry,tie,author,content," +
"href from poemtable";
try {
conn = DBHelper.getConnection();
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()){
poem = new Poem() ;
poem.setDynasty(rs.getString(1));
poem.setCategory(rs.getString(2));
poem.setTitle(rs.getString(3));
poem.setAuthor(rs.getString(4));
poem.setContent(rs.getString(5));
poem.setHref(rs.getString(6));
poemList.add(poem);
}
}catch (SQLException e){
e.printStackTrace();
throw  new SQLException("findAll failed");
}finally {
DBHelper.close(rs, ps, conn);
}
return poemList ;
}
}

step４

AppMain中的调用。

//store to mysql
PoemDao poemDao = new PoemDaoImpl() ;
for (Poem poem: poemList){
try {
poemDao.add(poem);
}catch (SQLException e){
e.printStackTrace();
}
}