重溫Java持久化(一)持久化

  09年和朋友，寫了個仿SSH的框架例子，將其三塊代碼集成（仿structs、仿spring、仿hibernate），並作了個小網站(JSTL+JSP+(仿)SSH)，採起這個框架，感受挺好用的。

主要目的是爲了提升對框架的認識，故沒有真正的SSH複雜，意在道明其因由，我的認爲，對於企業項目開發可以理解框架原理便可。

因仿hibernate的這塊代碼非本人所寫的，難免的有點點遺憾，前些日子無聊，又看到另個朋友採用註解寫了個小框架（針對android系統的），也想採用註解寫個試試。

通過幾天的折騰，也總算是出爐了。時間倉租，應該會有很多瑕疵，之後有時間，慢慢優化咯。

優勢:

1. 以對象方式操做數據庫，使用簡單方便.

2. 所依賴的jar包少，僅須要數據庫驅動的jar.

3. 以上兩個優勢，對於業務不復雜的小型系統來講，蠻方便的.

DMIS-JHibernate關鍵代碼 

DMIS-JHibernate.jar  DMIS-JHibernate_src.zip見附件

=====================================

先來看下註解的含義，見註釋

/* 

 * 元註解@Target,@Retention,@Documented,@Inherited 

 *  

 * @Target 表示該註解用於什麼地方，可能的 ElemenetType 參數包括： 

 *         ElemenetType.CONSTRUCTOR 構造器聲明 

 *         ElemenetType.FIELD 域聲明（包括 enum 實例） 

 *         ElemenetType.LOCAL_VARIABLE 局部變量聲明 

 *         ElemenetType.METHOD 方法聲明 

 *         ElemenetType.PACKAGE 包聲明 

 *         ElemenetType.PARAMETER 參數聲明 

 *         ElemenetType.TYPE 類，接口（包括註解類型）或enum聲明 

 *          

 * @Retention 表示在什麼級別保存該註解信息。可選的 RetentionPolicy 參數包括： 

 *         RetentionPolicy.SOURCE 註解將被編譯器丟棄 

 *         RetentionPolicy.CLASS 註解在class文件中可用，但會被VM丟棄 

 *         RetentionPolicy.RUNTIME VM將在運行期也保留註釋，所以能夠經過反射機制讀取註解的信息。 

 *          

 * @Documented 將此註解包含在 javadoc 中 

 *      

 * @Inherited 容許子類繼承父類中的註解 

 *    

 * @author ypf

 */

@Target(ElementType.TYPE)

@Retention(RetentionPolicy.RUNTIME)

@Documented

@Inherited

public @interface Table {

 /**

  * 表名

  * 

  * @return

  */

  public abstract String name();

}

=====================================

/**

 * 註解表 標識是否爲主鍵

 * @author ypf

 */

@Target(ElementType.FIELD)

@Retention(RetentionPolicy.RUNTIME)

@Documented

@Inherited

public abstract @interface Id {

}

=====================================

/**

 * 註解表 標識所映射的數據庫字段

 * 

 * @author ypf

 */

@Target(ElementType.FIELD)

@Retention(RetentionPolicy.RUNTIME)

@Documented

@Inherited

public abstract @interface Column {

 /**

  * 列名

  * @return String

  */

 public abstract String name();

 /**

  * 類型

  * @return String

  */

 public abstract String type() default "";

 /**

  * 類型

  * @return int

  */

 public abstract int length() default 0;

}

=====================================

/**

 * 數據庫輔助類

 * @author ypf

 */

public class DBHelper {

  Logger logger = Logger.getLogger(DBHelper.class.getName());

  private String driver;

  private String url;

  private String dbname;

  private String dbpass;

  public DBHelper(String driver, String url, String dbname, String dbpass) {

    super();

    this.driver = driver;

    this.url = url;

    this.dbname = dbname;

    this.dbpass = dbpass;

  }

  public Connection getConn() throws ClassNotFoundException, SQLException {

    Class.forName(driver);

    Connection conn = DriverManager.getConnection(url, dbname, dbpass);

    return conn;

 }

 /**

  * 釋放資源

  * 

  * @param conn-鏈接對象

  * @param pstmt-預編譯

  * @param rs-結果集

  */

  public void closeAll(Connection conn, PreparedStatement ps, ResultSet rs) {

    if (rs != null) {

      try {

        rs.close();

      } catch (SQLException e) {

        e.printStackTrace();

      }

    }

    if (ps != null) {

      try {

        ps.close();

      } catch (SQLException e) {

        e.printStackTrace();

      }

    }

    if (conn != null) {

      try {

        conn.close();

      } catch (SQLException e) {

        e.printStackTrace();

      }

    }

  }

 /**

  * 執行增、刪、改

  * @param sql-語句

  * @param params-數組型參數

  * @return int 受影響的行數

  * @throws SQLException

  * @throws ClassNotFoundException

  */

  public int executeUpdate(String sql, Object... params) throws SQLException, ClassNotFoundException {

    Connection connection = null;

    PreparedStatement ps = null;

    int num = 0;

    // 處理SQL，執行SQL

    try {

      connection = getConn(); // 獲得數據庫鏈接

      ps = connection.prepareStatement(sql); // 預處理SQL語句

      buildPreparedStatement(ps, params);

      logger.info("Oper: " + sql);

      num = ps.executeUpdate(); // 執行SQL語句

    }catch (SQLException e) {

      throw e;

    }catch (ClassNotFoundException e) {

      throw e;

    }finally {

      closeAll(connection, ps, null);

    }

    return num;

  }

 /**

  * 爲PreparedStatement對象填充參數

  * @param ps 預編譯句子

  * @param param 動態參數

  * @throws SQLException

  */

  public void buildPreparedStatement(PreparedStatement ps, Object... params) throws SQLException {

    // 設置參數

    for (int i = 0; i < params.length; i++) {

      // 將Date轉換成java.sql.Date

      if (params[i] instanceof Date) {

        Date d = (Date) params[i];

        ps.setObject(i + 1, new Timestamp(d.getTime()));

      } else {

        ps.setObject(i + 1, params[i]);

      }

    }

  }

 /**

  * 執行查詢操做

  * @param sql sql語句

  * @param param 動態參數

  * @return RowSet 結果集，可直接使用

  */

  public RowSet executeQuery(String sql, Object... params) throws SQLException, ClassNotFoundException {

    Connection connection = null;

    PreparedStatement ps = null;

    ResultSet rs = null;

    RowSet rowset = null;

    try {

      connection = this.getConn();

      ps = connection.prepareStatement(sql);

      buildPreparedStatement(ps, params);

      logger.info("Oper: " + sql);

      rs = ps.executeQuery();

      rowset = populate(rs);

    } catch (SQLException e) {

      throw e;

    } catch (ClassNotFoundException e) {

      throw e;

    } finally {

      closeAll(connection, ps, rs);

    }

    return rowset;

  }

 /**

  * 將ResultSet轉換爲RowSet對象

  * @param rs 數據集

  * @return RowSet

  */

  public RowSet populate(ResultSet rs) throws SQLException {

    CachedRowSetImpl crs = new CachedRowSetImpl();

    crs.populate(rs);

    return crs;

  }

 /**

  * 從RowSet中獲取列頭

  * @param rs 數據集

  * @return List

  */

  public List getRowSetColName(RowSet rs) throws SQLException {

    ArrayList collist = new ArrayList();

    for (int i = 0; i < rs.getMetaData().getColumnCount(); i++) {

      collist.add(rs.getMetaData().getColumnName(i + 1).toUpperCase());

    }

    return collist;

  }

}

=====================================

/**

 * 用於建立表的輔助類

 * 

 * @author ypf

 */

public class TableHelper {

  private Logger log = Logger.getLogger(TableHelper.class.getName());

  private Session session;

  public TableHelper(Session session) {

    this.session = session;

  }

 /**

  * 建立表 

  * @param <T>

  * @param clazz

  */

  public <T> void createTable(Class<T> clazz) {

    String tableName = "";

    if (clazz.isAnnotationPresent(Table.class)) {

      Table table = (Table) clazz.getAnnotation(Table.class);

      tableName = table.name();

    } else {

      return;

    }

    StringBuilder sb = new StringBuilder();

    // 用來判斷表是否存在，若是存在則不執行改操做

    sb.append("CREATE TABLE ").append(tableName).append(" (");

    List<Field> allFields = ClassUtil.joinFields(clazz);

    for (Field field : allFields) {

      if (!field.isAnnotationPresent(Column.class)) {

        continue;

      }

      Column column = (Column) field.getAnnotation(Column.class);

      String columnType = "";

      // 判斷column的type字段是否爲空，若是爲空則根據字段的值將其轉換爲對應的數據庫類型

      if (column.type().equals(""))

        columnType = getColumnType(field.getType());

      else {

        columnType = getColumnType(column.type());

      }

      sb.append(column.name() + " " + columnType);

      if (column.length() != 0) {

        sb.append("(" + column.length() + ")");

      }

      // 添加主鍵

      if (field.isAnnotationPresent(Id.class)) {

        sb.append(" PRIMARY KEY");

      }

      sb.append(", ");

    }

    sb.delete(sb.length() - 2, sb.length() - 1);

    sb.append(")");

    String sql = sb.toString();

    String checkSql = "SELECT 1 FROM USER_TABLES WHERE TABLE_NAME=?";

    String dropSql = "DROP TABLE " + tableName.toUpperCase();

    try {

      RowSet rs = session.executeQuery(checkSql, tableName.toUpperCase());

      // 若是存在則先刪除

      if (rs.next()) {

        log.info("表[" + tableName.toUpperCase() + "]已經存在!");

        // session.executeUpdate(dropSql);

        // session.executeUpdate(sql);

      } else {

        session.executeUpdate(sql);

        log.info("表[" + tableName.toUpperCase() + "]建立成功!");

      }

    } catch (SQLException e) {

      e.printStackTrace();

    } catch (ClassNotFoundException e) {

      e.printStackTrace();

    }

  }

  //根據字段類型返回數據庫對應的列，之後須要擴展優化，一遍支持多中數據庫，目前只支持oracle

  private String getColumnType(Class<?> fieldType) {

    if (String.class == fieldType) {

      return "VARCHAR";

    }

    if ((Integer.TYPE == fieldType) || (Integer.class == fieldType)) {

      return "NUMBER";

    }

    if ((Long.TYPE == fieldType) || (Long.class == fieldType)) {

      return "LONG";

    }

    if ((Float.TYPE == fieldType) || (Float.class == fieldType)) {

      return "NUMBER";

    }

    if ((Double.TYPE == fieldType) || (Double.class == fieldType)) {

      return "NUMBER";

    }

    if (Blob.class == fieldType) {

      return "BLOB";

    }

    if (Date.class == fieldType) {

     return "DATE";

    }

    return "VARCHAR";

  }

 /**

  * 根據傳入的類型返回對應的數據庫字段類型 若是找不到匹配的則直接用其自己做爲數據庫列類型(type不容許爲空)

  * 備註：這裏之後會擴展（根據不用的數據庫建立不用的字段）

  * @param type

  * @return String

  */

  private String getColumnType(String type) {

    if (ColumnType.INTEGER.equals(type)) {

      return "NUMBER";

    }

    if (ColumnType.STRING.equals(type)) {

      return "VARCHAR";

    }

    if (ColumnType.LONG.equals(type)) {

      return "LONG";

    }

    return type;

  }

}

=====================================

/**

 * 對外公開的數據庫訪問類

 * 

 * @author ypf

 */

public interface Session {

 /**

  * 類加載 

  */

  public abstract void loadContext(ClassLoad c);

 /**

  * 添加 

  */

  public abstract Serializable insert(Object entity) throws IllegalArgumentException, SecurityException, IllegalAccessException, NoSuchFieldException, Exception;

 /**

  * 刪除

  */

  public abstract Serializable delete(Object entity) throws SQLException, ClassNotFoundException;

 /**

  * 修改

  */

  public abstract Serializable update(Object entity) throws SQLException, ClassNotFoundException, IllegalArgumentException, SecurityException, IllegalAccessException, InvocationTargetException, NoSuchMethodException;

 /**

  * 根據id獲取對象

  */

  public abstract Object getResource(Serializable id, Class clazz) throws SQLException, ClassNotFoundException, InstantiationException, IllegalAccessException;

 /**

  * 查詢全部

  */

  public abstract List query(Class clazz) throws SQLException, ClassNotFoundException, InstantiationException, IllegalAccessException;

 /**

  * 封裝執行sql代碼.

  */

  public int executeUpdate(String sql, Object... params) throws SQLException, ClassNotFoundException;

 /**

  * 經過sql語句,進行查詢操做

  * @param sql sql預警

  * @param params 參數

  * @return RowSet

  */

  public RowSet executeQuery(String sql, Object... params) throws SQLException, ClassNotFoundException;

 /**

  * 經過sql語句,進行增、刪、改操做

  * @param sql sql預警

  * @param params 參數

  * @return RowSet

  */

  public Object executeQueryUnique(String sql, Object... params) throws SQLException, ClassNotFoundException;

 //未完待續...

}

=====================================

/**

 * 提供CRUD操做的實現類

 * @author ypf

 */

public class SessionImpl implements Session {

  private Logger log = Logger.getLogger(SessionImpl.class.getName());

  DBHelper dbHelper; // 數據庫訪問類

  Class clazz; // 當前處理對象

  String tableName; // 代表

  List<Field> allFields; // 全部字段

  String keyName; // 主鍵

  public void loadContext(ClassLoad c) {

    c.execute();

  }

 /**

  * 構建列信息,如：name,type

  * @return String

  */

  private String buildStrColumn() {

    String step = "";

    for (int i = 0; i < allFields.size(); i++) {

      Column column = (Column) allFields.get(i).getAnnotation(Column.class);

      step += column.name() + ",";

    }

    if (step.length() > 0)

      step = step.substring(0, step.length() - 1);

    }else {

      step = "*";

    }

    return step;

  }

 /**

  * 構建參數信息,如：?,?

  * @return String

  */

  private String buildValColumn() {

    String step = "";

    for (int i = 0; i < allFields.size(); i++) {

      step += "?,";

    }

    if (step.length() > 0)

      step = step.substring(0, step.length() - 1);

    return step;

 }

 /**

  * 初始化

  * 

  * @param clazz

  */

  private void initProperites(Class clazz) {

    this.clazz = clazz;

    if (this.clazz.isAnnotationPresent(Table.class)) {

      Table table = (Table) clazz.getAnnotation(Table.class);

      this.tableName = table.name();

    }

    this.allFields = ClassUtil.joinFields(clazz);

    for (Field field : allFields) {

      if (!field.isAnnotationPresent(Column.class)) {

        continue;

      }

      Column column = (Column) field.getAnnotation(Column.class);

      if (field.isAnnotationPresent(Id.class)) {

        this.keyName = field.getName();

      }

    }

    log.info("clazz:" + this.clazz + " tableName:" + this.tableName + " keyName:" + this.keyName);

  }

  public SessionImpl(DBHelper dbHelper) {

    this.dbHelper = dbHelper;

  }

  @Override

  public Serializable delete(Object entity) throws SQLException, ClassNotFoundException {

    initProperites(entity.getClass());

    Object keyValue = ClassUtil.getPropertie(entity, keyName);

    String sql = "delete from {0} where {1}=?".replace("{0}", this.tableName).replace("{1}", keyName);

    log.info("[delete]:" + sql);

    log.info("[params]:" + keyValue);

    return dbHelper.executeUpdate(sql, keyValue);

  }

  @Override

  public Object getResource(Serializable id, Class clazz) throws SQLException, ClassNotFoundException, InstantiationException, IllegalAccessException {

    initProperites(clazz);

    String cols = buildStrColumn();

    String sql = ClassUtil.formartString("SELECT {0} FROM {1} where {2}=?", new String[] { cols, this.tableName, this.keyName });

    log.info("[get]:" + sql);

    log.info("[params]:" + id);

    RowSet rs = dbHelper.executeQuery(sql, id);

    List list = ClassUtil.buildEntities(rs, clazz, allFields);

    if (list.size() > 0)

      return list.get(0);

    return null;

  }

  // 插入

  @Override

  public Serializable insert(Object entity) throws Exception {

    initProperites(entity.getClass());

    String cols = buildStrColumn();// 要查詢的字段

    String vs = buildValColumn();// 預編譯參數

    String sql = ClassUtil.formartString("insert into {0}({1}) values({2})", new String[] { this.tableName, cols, vs });

    Object[] params = ClassUtil.buildParams(entity, allFields);

    return dbHelper.executeUpdate(sql, params);

  }

  @Override

  public Serializable update(Object entity) throws SQLException, ClassNotFoundException, IllegalArgumentException, SecurityException, IllegalAccessException, InvocationTargetException, NoSuchMethodException {

    initProperites(entity.getClass());

    String cols = buildStrColumn();

    String vs = buildValColumn();

    String _cols = (cols + ",").replace(",", "=?,");

    _cols = _cols.length() > 0 ? _cols.substring(0, _cols.length() - 1) : "*";

    Object[] params = ClassUtil.buildParams(entity, allFields);

    Object vKey = ClassUtil.buildParams(entity, keyName);

    Object[] _params = new Object[params.length + 1];

    for (int i = 0; i < params.length; i++) {

     _params[i] = params[i];

    }

    _params[params.length] = vKey.toString();

    String sql = ClassUtil.formartString("update {0} set {1} where {2}=? ", new String[] { this.tableName, _cols, this.keyName });

    return dbHelper.executeUpdate(sql, _params);

  }

  @Override

  public List query(Class clazz) throws SQLException, ClassNotFoundException, InstantiationException, IllegalAccessException {

    initProperites(clazz);

    String cols = buildStrColumn();

    String sql = ClassUtil.formartString("SELECT {0} FROM {1}", new String[] { cols, this.tableName });

    RowSet rs = dbHelper.executeQuery(sql);

    List list = ClassUtil.buildEntities(rs, clazz, allFields);

    return list;

  }

  @Override

  public int executeUpdate(String sql, Object... params) throws SQLException, ClassNotFoundException {

    return dbHelper.executeUpdate(sql, params);

  }

  @Override

  public RowSet executeQuery(String sql, Object... params) throws SQLException, ClassNotFoundException {

    return dbHelper.executeQuery(sql, params);

  }

  @Override

  public Object executeQueryUnique(String sql, Object... params) throws SQLException, ClassNotFoundException {

    RowSet rs = dbHelper.executeQuery(sql, params);

      if (rs.next())

        return rs.getObject(1);

    return null;

  }

}

=====================================

/**

 * 輔助類

 * @author ypf

 */

public class ClassUtil {

 /**

  * 合併Field數組並去重,並實現過濾掉非Column字段,和實現Id放在首字段位置功能

  * @param clazz

  * @return 因此字段

  */

  public static List<Field> joinFields(Class clazz) {

    List<Class> cList = new ArrayList();

    List<Field> fList = new ArrayList();

    // 獲取全部類

    findAllClass(clazz, cList);

    // 獲取全部字段

    for (Class c : cList) {

      for (int i = 0; i < c.getDeclaredFields().length; i++) {

        fList.add(c.getDeclaredFields()[i]);

      }

    }

    Map<String, Field> map = new LinkedHashMap<String, Field>();

    for (Field field : fList) {

     // 過濾掉非Column定義的字段

     if (!field.isAnnotationPresent(Column.class)) {

      continue;

     }

     Column column = (Column) field.getAnnotation(Column.class);

     map.put(column.name(), field);

    }

    List<Field> list = new ArrayList<Field>();

    for (String key : map.keySet()) {

      Field step = map.get(key);

      // 若是是Id則放在首位置.

      if (step.isAnnotationPresent(Id.class)) {

        list.add(0, step);

      } else {

        list.add(step);

      }

    }

    return list;

   }

 /**

  * 查找全部類：自身及全部的父類(接口除外)

  * 

  * @param clazz

  * @param list

  */

  private static void findAllClass(Class<?> clazz, List list) {

    // 添加自身Class

    if (list.size() == 0)

    list.add(clazz);

    Class<?> c = clazz.getSuperclass();

    if (c != null) {

     list.add(c);

     findAllClass(c, list);

    }

  }

 /**

  * 建立類及封裝屬性

  * @param clazz

  * @param fileds

  * @param values

  * @return size

  */

  public static Object buildProperties(Class clazz, List<Field> fileds, List values) throws InstantiationException, IllegalAccessException {

    if (values.size() != fileds.size())

      throw new RuntimeException("fileds的size和values的size不一致！");

    Object obj = clazz.newInstance();

    for (int i = 0; i < fileds.size(); i++) {

      buildPropertie(obj, fileds.get(i), values.get(i));

    }

    return obj;

  }

 /**

  * 給對象的某個字段封裝數值

  */

  public static void buildPropertie(Object obj, Field f, Object value) {

    try {

       String methodName = buildSetMethod(f.getName());

       // 給某個字段封裝數值，methodName方法名，obj.getClass().getMethod(buildGetMethod(f.getName())).getReturnType()返回類型

       // invoke執行方法,obj要賦值的對象,value要賦的值

       obj.getClass().getMethod(methodName, obj.getClass().getMethod(buildGetMethod(f.getName())).getReturnType()).invoke(obj, value);

    } catch (Exception e) {

      e.printStackTrace();

    }

  }

 /**

  * 構建get方法

  * @param fieldName

  * @return String

  */

  public static String buildGetMethod(String fieldName) {

    String methodName = "get" + fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);

    return methodName;

  }

 /**

  * 構建set方法

  * @param fieldName

  * @return String

  */

  public static String buildSetMethod(String fieldName) {

    String methodName = "set" + fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);

    return methodName;

  }

 /**

  * 根據字段名或對象對應的get方法值

  * @param obj 對象

  * @param fieldName字段名

  * @return Object

  */

  public static Object getPropertie(Object obj, String fieldName) {

    Object val = "";

    try {

      String methodName = buildGetMethod(fieldName);

      val = obj.getClass().getMethod(methodName).invoke(obj);

    } catch (Exception e) {

      e.printStackTrace();

    }

    return val;

 }

 /**

  * 根據字段獲取對應的值

  * @param entity

  * @param allFields

  * @return Object[]

  */

  public static Object[] buildParams(Object entity, List<Field> fields) throws IllegalArgumentException, SecurityException, IllegalAccessException, InvocationTargetException, NoSuchMethodException {

    Object[] params = new Object[fields.size()];// 字段參數值

    for (int i = 0; i < fields.size(); i++) {

      Field f = fields.get(i);

     String methodName = ClassUtil.buildGetMethod(f.getName());

      Object v = entity.getClass().getMethod(methodName).invoke(entity);

      if (v instanceof Enum) {

        v = ((Enum) v).ordinal();

      }

      params[i] = v;

      }

    return params;

  }

  public static Object buildParams(Object entity, Field field) throws IllegalArgumentException, SecurityException, IllegalAccessException, InvocationTargetException, NoSuchMethodException {

    String methodName = ClassUtil.buildGetMethod(field.getName());

    Object v = entity.getClass().getMethod(methodName).invoke(entity);

    return v;

  }

  public static Object buildParams(Object entity, String fieldName) throws IllegalArgumentException, SecurityException, IllegalAccessException, InvocationTargetException, NoSuchMethodException {

    String methodName = ClassUtil.buildGetMethod(fieldName);

    Object v = entity.getClass().getMethod(methodName).invoke(entity);

    return v;

  }

 /**

  * 格式化

  * @param str

  * @param params

  * @return String

  */

  public static String formartString(String str, Object... params) {

    for (int i = 0; i < params.length; i++) {

    Object obj = params[i];

    if (obj != null)

      str = str.replace("{" + i + "}", obj.toString());

    }

   return str;

  }

  public static List buildEntities(RowSet rs, Class clazz, List<Field> allFields) throws SQLException, InstantiationException, IllegalAccessException {

    List<String> listCols = getRowSetColName(rs);

    List list = new ArrayList();

    while (rs.next()) {

      List values = new ArrayList();

      for (String key : listCols) {

        values.add(rs.getObject(key));

      }

      Object obj = ClassUtil.buildProperties(clazz, allFields, values);

      list.add(obj);

    }

    return list;

  }

  public static List getRowSetColName(RowSet rs) throws SQLException {

    List collist = new ArrayList();

    for (int i = 0; i < rs.getMetaData().getColumnCount(); i++) {

      collist.add(rs.getMetaData().getColumnName(i + 1).toUpperCase());

    }

    return collist;

  }

}