Java数据实体模型:构造通用类型
我在静态方法中使用常规类型时遇到了一些问题 欢迎对源代码的所有评论,尤其是那些显著改进代码的评论。我目前也不打算使用任何外部框架,除了JDBC,以保持它仍然简单,请不要太强调这一点 我不使用外部框架的观点也得到了以下事实的支持:我将在数据库上使用的操作非常少:Java数据实体模型:构造通用类型,java,refactoring,Java,Refactoring,我在静态方法中使用常规类型时遇到了一些问题 欢迎对源代码的所有评论,尤其是那些显著改进代码的评论。我目前也不打算使用任何外部框架,除了JDBC,以保持它仍然简单,请不要太强调这一点 我不使用外部框架的观点也得到了以下事实的支持:我将在数据库上使用的操作非常少: 插入数据 更新数据 正在检索所有字段。(只需输入不同的SQL查询,您就可以选择要检索的字段 我不打算制作一个完整的框架,所以我知道它不会支持所有内容。检索所有字段的速度也不是一个真正的问题,因为这几乎只在服务器启动时完成,如果在任何其
- 插入数据
- 更新数据
- 正在检索所有字段。(只需输入不同的SQL查询,您就可以选择要检索的字段
abstract public class Entity<KeyType, DataType> {
protected KeyType key;
protected List<Object> data;
public Entity() {
data = new ArrayList<>();
}
//abstract public static Map<KeyType, DataType> getAll();
protected List<Object> createData(final DataAction dataAction) {
List<Object> list = new ArrayList<>();
if (dataAction == DataAction.INSERT) {
list.add(key);
}
list.addAll(data);
if (dataAction == DataAction.UPDATE) {
list.add(key);
}
return list;
}
abstract public void insert();
abstract public void update();
protected static <KeyType, DataType> Map<KeyType, DataType> getData(final Class<DataType> dataTypeClass, final String query) {
Map<KeyType, DataType> map = new HashMap<>();
try {
PreparedStatement preparedStatement = DatabaseConnection.getConnection().prepareStatement(query);
ResultSet resultSet = preparedStatement.executeQuery();
while (resultSet.next()) {
KeyType key = (KeyType)resultSet.getObject(1);
int index = 2;
List<Object> dataList = new ArrayList<>();
while (resultSet.getObject(index) != null) {
dataList.add(resultSet.getObject(index));
index++;
}
DataType dataObject = null;
try {
dataObject = dataTypeClass.getConstructor(List.class).newInstance(dataList);
} catch (InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException | NoSuchMethodException | SecurityException ex) {
Logger.getLogger(Entity.class.getName()).log(Level.SEVERE, null, ex);
}
map.put(key, dataObject);
}
} catch (SQLException ex) {
Logger.getLogger(Entity.class.getName()).log(Level.SEVERE, null, ex);
}
return map;
}
protected void executeQuery(final String query, final List<Object> data) {
try {
PreparedStatement preparedStatement = DatabaseConnection.getConnection().prepareStatement(query);
int dataIndex = 0;
for (Object dataObject : data) {
preparedStatement.setObject(dataIndex, dataObject);
dataIndex++;
}
preparedStatement.execute();
preparedStatement.close();
} catch (SQLException ex) {
Logger.getLogger(Entity.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
抽象公共类实体{
受保护的密钥类型密钥;
受保护名单数据;
公共实体(){
数据=新的ArrayList();
}
//抽象公共静态映射getAll();
受保护列表createData(最终DataAction DataAction){
列表=新的ArrayList();
if(dataAction==dataAction.INSERT){
列表。添加(键);
}
list.addAll(数据);
if(dataAction==dataAction.UPDATE){
列表。添加(键);
}
退货清单;
}
抽象公共空间插入();
抽象公共空间更新();
受保护的静态映射getData(最终类dataTypeClass,最终字符串查询){
Map Map=newhashmap();
试一试{
PreparedStatement PreparedStatement=DatabaseConnection.getConnection().prepareStatement(查询);
ResultSet ResultSet=preparedStatement.executeQuery();
while(resultSet.next()){
KeyType key=(KeyType)resultSet.getObject(1);
int指数=2;
List dataList=new ArrayList();
while(resultSet.getObject(index)!=null){
add(resultSet.getObject(index));
索引++;
}
数据类型dataObject=null;
试一试{
dataObject=dataTypeClass.getConstructor(List.class).newInstance(dataList);
}catch(实例化异常| IllegalAccessException | IllegalArgumentException | InvocationTargetException | NoSuchMethodException | SecurityException ex){
Logger.getLogger(Entity.class.getName()).log(Level.SEVERE,null,ex);
}
map.put(key,dataObject);
}
}catch(SQLException-ex){
Logger.getLogger(Entity.class.getName()).log(Level.SEVERE,null,ex);
}
返回图;
}
受保护的void executeQuery(最终字符串查询、最终列表数据){
试一试{
PreparedStatement PreparedStatement=DatabaseConnection.getConnection().prepareStatement(查询);
int-dataIndex=0;
for(对象数据对象:数据){
setObject(dataIndex,dataObject);
dataIndex++;
}
preparedStatement.execute();
preparedStatement.close();
}catch(SQLException-ex){
Logger.getLogger(Entity.class.getName()).log(Level.SEVERE,null,ex);
}
}
}
具体实现Account.java:
public class Account extends Entity<String, Account> {
private final static String SELECT_ALL_QUERY = "SELECT * FROM accounts";
private final static String INSERT_QUERY = "INSERT INTO accounts (username, password) VALUES(?, ?)";
private final static String UPDATE_QUERY = "UPDATE accounts SET password=? WHERE username=?";
private String username;
private String password;
public Account(final String username, final String password) {
this.username = username;
this.password = password;
key = username;
data.add(password);
}
public Account(final List<Object> data) {
this((String)data.get(0), (String)data.get(1));
}
public String getUsername() {
return username;
}
public void setUsername(final String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(final String password) {
this.password = password;
}
public static Map<String, Account> selectAll() {
return getData(Account.class, SELECT_ALL_QUERY);
}
@Override
public void insert() {
executeQuery(INSERT_QUERY, createData(DataAction.INSERT));
}
@Override
public void update() {
executeQuery(UPDATE_QUERY, createData(DataAction.UPDATE));
}
}
公共类帐户扩展实体{
私有最终静态字符串SELECT\u ALL\u QUERY=“SELECT*FROM accounts”;
私有最终静态字符串INSERT_QUERY=“插入帐户(用户名、密码)值(?,)”;
私有最终静态字符串UPDATE_QUERY=“更新帐户设置密码=?其中用户名=?”;
私有字符串用户名;
私有字符串密码;
公共帐户(最终字符串用户名、最终字符串密码){
this.username=用户名;
this.password=密码;
密钥=用户名;
数据。添加(密码);
}
公共账户(最终清单数据){
这个((String)data.get(0),(String)data.get(1));
}
公共字符串getUsername(){
返回用户名;
}
public void setUsername(最终字符串用户名){
this.username=用户名;
}
公共字符串getPassword(){
返回密码;
}
public void setPassword(最终字符串密码){
this.password=密码;
}
公共静态映射selectAll(){
返回getData(Account.class,选择所有查询);
}
@凌驾
公开作废插入(){
executeQuery(插入查询,createData(DataAction.INSERT));
}
@凌驾
公共无效更新(){
executeQuery(UPDATE_QUERY,createData(DataAction.UPDATE));
}
}
我对具体的实现总体上很满意,似乎我已经设法将其降至最低,除了公共帐户(最终列表数据)
似乎不太好,但我可以接受它
然而,正如所猜测的,来自实体的getData()
肯定不好,如果可能的话,我想对其进行改进
我想使用的是类似于datatypedataobject=newdatatype(dataList)
的东西,但似乎无法实例化泛型类型参数
那么,在我当前的视图中,有没有任何方法可以优化我当前的代码?有没有可能进一步解耦具体类和抽象类
编辑:
增加了一个相关的问题(我不认为我应该为这件事提出一个全新的问题,对吗?)
是否有办法将静态字符串(SQL查询)和insert()
和update()
从Account类移到Entity类中?以避免
public static Map<String, Account> selectAll()
{
return getData(
new EntityFactory<Account>()
{
public Account newInstance(ResultSet resultSet) throws SQLException
{
return new Account(resultSet.getString(0), resultSet.getString(1));
}
},
SELECT_ALL_QUERY
);
}
protected static <K, T extends Entity<K>> Map<K, T> getData(EntityFactory<T> entityFactory, String query)
{
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try
{
connection = dataSource.getConnection();
preparedStatement = connection.prepareStatement(query);
resultSet = preparedStatement.executeQuery();
Map<K, T> entities = new HashMap<>();
while (resultSet.next())
{
Entity<K> entity = entityFactory.newInstance(resultSet);
entities.put(entity.getKey(), entity);
}
return entities;
}
finally
{
closeQuietly(resultSet);
closeQuietly(prepareStatement);
closeQuietly(connection);
}
}
public interface Entity<K>
{
public K getKey();
}
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try
{
connection = //get connection from pool or single instance.
preparedStatement = connection.prepareStatement("SELECT * FROM table WHERE column = ?");
preparedStatement.setString(1, "some string");
resultSet = preparedStatement.executeQuery();
while (resultSet.next())
{
//logic goes here.
}
}
catch (SQLException e)
{
//Handle exceptions.
}
finally
{
closeQuietly(resultSet);
closeQuietly(prepareStatement);
closeQuietly(connection);
}
try
{
if (resultSet != null)
{
resultSet.close();
}
}
catch (SQLException e)
{
//Log exceptions but don't re-throw.
}
public interface RecordMapper<KeyType, DataType extends Entity> {
public void appendToMap(ResultSet resultSet, Map<KeyType, DataType>) throws SQLException;
}
public class AccountMapper implement RecordMapper<String, Account>{
public void appendToMap(ResultSet resultSet, Map<String, Account> accounts) throws SQLException {
String user= resultSet.getString("userName");
String pwd= resultSet.getString("passWord");
Account account = new Account(user, pwd);
accounts.put(user, account);
}
}
public <KeyType, DataType> Map<KeyType, DataType> getData(final RecordMapper<KeyType, DataType> mapper, final String query) {
Map<KeyType, DataType> map = new HashMap<>();
try {
PreparedStatement preparedStatement = DatabaseConnection.getConnection().prepareStatement(query);
ResultSet resultSet = preparedStatement.executeQuery();
while (resultSet.next()) {
mapper.appendToMap(resultSet, map);
}
} catch (SQLException ex) {
Logger.getLogger(Entity.class.getName()).log(Level.SEVERE, null, ex);
} finally {
if(resultSet != null){
try{resultSet.close();} catch (Exception e){}
}
if(preparedStatement!= null){
try{preparedStatement.close();} catch (Exception e){}
}
}
return map;
}
public void executeQuery(final String query, final List<Object> data) {
try {
PreparedStatement preparedStatement = DatabaseConnection.getConnection().prepareStatement(query);
int dataIndex = 0;
for (Object dataObject : data) {
preparedStatement.setObject(dataIndex, dataObject);
dataIndex++;
}
preparedStatement.execute();
} catch (SQLException ex) {
Logger.getLogger(Entity.class.getName()).log(Level.SEVERE, null, ex);
} finally {
if(resultSet != null){
try{resultSet.close();} catch (Exception e){}
}
if(preparedStatement!= null){
try{preparedStatement.close();} catch (Exception e){}
}
}
}
}