java db 使用_JavaDB的基本使用[通俗易懂]

Derby並不是一個新的數據庫產品,它是由IBM捐獻給Apache的DB項目的一個純Java數據庫,JDK6.0里面帶的這個Derby的版本是10.2.1.7,支持存儲過程和觸發器;有兩種運行模式,一種是作為嵌入式數據庫,另一種是作為網絡數據庫,前者的數據庫服務器和客戶端都在同一個JVM里面運行,后者允許數據庫服務器端和客戶端不在同一個JVM里面,而且允許這兩者在不同的物理機器上.值得注意的是JDK6里面的這個Derby支持JDK6的新特性JDBC 4.0規范(JSR 221),現在我們如果要練習JDBC的用法,沒有必要單獨裝一個數據庫產品了,直接用Derby就行.

下面是個使用derby的簡單例子:

首先導入JAR包:derby.jar,如果你裝的是JDK6,在C:/Program Files/Sun/JavaDB/lib目錄下就可以找到.

然后就要創建數據庫了:

Java代碼

privateConnection getConnection()throwsSQLException {

Connection connection = DriverManager

.getConnection(“jdbc:derby:userDB;create=true;user=test;password=test”);

connection.setAutoCommit(false);

returnconnection;

}private Connection getConnection() throws SQLException {

Connection connection = DriverManager

.getConnection(“jdbc:derby:userDB;create=true;user=test;password=test”);

connection.setAutoCommit(false);

return connection;

}

其中userDB是要連接數據庫的名字,create=true表示如果該數據庫不存在,則創建該數據庫,如果數據庫存在,則用用戶user=test;密碼password=test連接數據庫.

有了數據庫,接下來該建表了:

Java代碼

privatevoidcreateTable(Connection connection)throwsSQLException {

Statement statement = connection.createStatement();

String sql =”create table USERS(“

+”   ID                           BIGINT                       not null generated by default as identity,”

+”   USER_NAME            VARCHAR(20)            not null,”

+”   PASSWORD             VARCHAR(20),”

+”   constraint P_KEY_1 primary key (ID))”;

statement.execute(sql);

sql =”create unique index USER_NAME_INDEX on USERS (“

+”   USER_NAME            ASC)”;

statement.execute(sql);

statement.close();

}private void createTable(Connection connection) throws SQLException {

Statement statement = connection.createStatement();

String sql = “create table USERS(“

+ ” ID BIGINT not null generated by default as identity,”

+ ” USER_NAME VARCHAR(20) not null,”

+ ” PASSWORD VARCHAR(20),”

+ ” constraint P_KEY_1 primary key (ID))”;

statement.execute(sql);

sql = “create unique index USER_NAME_INDEX on USERS (“

+ ” USER_NAME ASC)”;

statement.execute(sql);

statement.close();

}

創建了USERS表,包括ID,USER_NAME,PASSWORD三個列,其中ID是主鍵,其中generated by default as identity的作用類似sequence,identity是定義自動加一的列,

GENERATED BY ALWAYS AS IDENTITY

GENERATED BY DEFAULT AS IDENTITY

By always和by default是說明生成這個IDENTITY的方式。

By always是完全由系統自動生成。

by default是可以由用戶來指定一個值。

編寫與USERS表對應的javabean(這個就不多說了),:

Java代碼

publicclassUserimplementsSerializable {

/**

*

*/

privatestaticfinallongserialVersionUID = 1L;

privateLong id;

privateString userName;

privateString password;

publicLong getId() {

returnid;

}

publicvoidsetId(Long id) {

this.id = id;

}

publicString getUserName() {

returnuserName;

}

publicvoidsetUserName(String userName) {

this.userName = userName;

}

publicString getPassword() {

returnpassword;

}

publicvoidsetPassword(String password) {

this.password = password;

}

}public class User implements Serializable {

/**

*

*/

private static final long serialVersionUID = 1L;

private Long id;

private String userName;

private String password;

public Long getId() {

return id;

}

public void setId(Long id) {

this.id = id;

}

public String getUserName() {

return userName;

}

public void setUserName(String userName) {

this.userName = userName;

}

public String getPassword() {

return password;

}

public void setPassword(String password) {

this.password = password;

}

}

接下來就可以就數據庫進行增刪改查的操作了:

插入數據:

Java代碼

privatevoidcreate(User user) {

Connection connection =null;

try{

connection =this.getConnection();

PreparedStatement statement = connection

.prepareStatement(“insert into users (user_name,password) values(?,?)”);

intindex =1;

statement.setString(index++, user.getUserName());

statement.setString(index++, user.getPassword());

statement.execute();

user.setId(this.getId(connection));

connection.commit();

}catch(SQLException e) {

rollback(connection);

thrownewRuntimeException(e);

}finally{

if(connection !=null) {

close(connection);

}

}

}private void create(User user) {

Connection connection = null;

try {

connection = this.getConnection();

PreparedStatement statement = connection

.prepareStatement(“insert into users (user_name,password) values(?,?)”);

int index = 1;

statement.setString(index++, user.getUserName());

statement.setString(index++, user.getPassword());

statement.execute();

user.setId(this.getId(connection));

connection.commit();

} catch (SQLException e) {

rollback(connection);

throw new RuntimeException(e);

} finally {

if (connection != null) {

close(connection);

}

}

}

Java代碼

privateLong getId(Connection connection)throwsSQLException {

CallableStatement callableStatement = connection

.prepareCall(“values identity_val_local()”);

ResultSet resultSet = callableStatement.executeQuery();

resultSet.next();

Long id = resultSet.getLong(1);

resultSet.close();

callableStatement.close();

returnid;

}private Long getId(Connection connection) throws SQLException {

CallableStatement callableStatement = connection

.prepareCall(“values identity_val_local()”);

ResultSet resultSet = callableStatement.executeQuery();

resultSet.next();

Long id = resultSet.getLong(1);

resultSet.close();

callableStatement.close();

return id;

}

getId方法是獲得系統默認的id值,是通過identity_val_local()獲得的,而函數IDENTITY_VAL_LOCAL()則可以在INSERT語句執行之后，為我們返回剛才系統為id所產生的值.感覺還是有點想sequence的curr_val.

修改數據:

Java代碼

privatevoidupdate(User user) {

Connection connection =null;

try{

connection =this.getConnection();

PreparedStatement statement = connection

.prepareStatement(“update users set user_name=?,password=? where id=?”);

intindex =1;

statement.setString(index++, user.getUserName());

statement.setString(index++, user.getPassword());

statement.setLong(index++, user.getId());

statement.execute();

connection.commit();

}catch(SQLException e) {

rollback(connection);

thrownewRuntimeException(e);

}finally{

if(connection !=null) {

close(connection);

}

}

}private void update(User user) {

Connection connection = null;

try {

connection = this.getConnection();

PreparedStatement statement = connection

.prepareStatement(“update users set user_name=?,password=? where id=?”);

int index = 1;

statement.setString(index++, user.getUserName());

statement.setString(index++, user.getPassword());

statement.setLong(index++, user.getId());

statement.execute();

connection.commit();

} catch (SQLException e) {

rollback(connection);

throw new RuntimeException(e);

} finally {

if (connection != null) {

close(connection);

}

}

}

刪除數據:

Java代碼

publicvoiddelete(Long id) {

Connection connection =null;

try{

connection =this.getConnection();

PreparedStatement statement = connection

.prepareStatement(“delete from users where id=?”);

statement.setLong(1, id);

statement.execute();

connection.commit();

}catch(SQLException e) {

rollback(connection);

thrownewRuntimeException(e);

}finally{

if(connection !=null) {

close(connection);

}

}

}public void delete(Long id) {

Connection connection = null;

try {

connection = this.getConnection();

PreparedStatement statement = connection

.prepareStatement(“delete from users where id=?”);

statement.setLong(1, id);

statement.execute();

connection.commit();

} catch (SQLException e) {

rollback(connection);

throw new RuntimeException(e);

} finally {

if (connection != null) {

close(connection);

}

}

}

查詢數據:

Java代碼

publicUser findById(Long id) {

Connection connection =null;

try{

connection =this.getConnection();

PreparedStatement statement = connection

.prepareStatement(“select user_name,password from users where id=?”);

statement.setLong(1, id);

ResultSet resultSet = statement.executeQuery();

User user =null;

if(resultSet.next()) {

user =newUser();

user.setId(id);

user.setUserName(resultSet.getString(“user_name”));

user.setPassword(resultSet.getString(“password”));

}

resultSet.close();

statement.close();

connection.commit();

returnuser;

}catch(SQLException e) {

thrownewRuntimeException(e);

}finally{

if(connection !=null) {

close(connection);

}

}

}public User findById(Long id) {

Connection connection = null;

try {

connection = this.getConnection();

PreparedStatement statement = connection

.prepareStatement(“select user_name,password from users where id=?”);

statement.setLong(1, id);

ResultSet resultSet = statement.executeQuery();

User user = null;

if (resultSet.next()) {

user = new User();

user.setId(id);

user.setUserName(resultSet.getString(“user_name”));

user.setPassword(resultSet.getString(“password”));

}

resultSet.close();

statement.close();

connection.commit();

return user;

} catch (SQLException e) {

throw new RuntimeException(e);

} finally {

if (connection != null) {

close(connection);

}

}

}

以上就是derby的簡單操作.