java db 使用_JavaDB的基本使用
Derby并不是一个新的数据库产品,它是由IBM捐献给Apache的DB项目的一个纯Java数据库,JDK6.0里面带的这个Derby的版本是10.2.1.7,支持存储过程和触发器;有两种运行模式,一种是作为嵌入式数据库,另一种是作为网络数据库,前者的数据库服务器和客户端都在同一个JVM里面运行,后者允许数据库服务器端和客户端不在同一个JVM里面,而且允许这两者在不同的物理机器上.值得注意的是JDK6里面的这个Derby支持JDK6的新特性JDBC 4.0规范(JSR 221),现在我们如果要练习JDBC的用法,没有必要单独装一个数据库产品了,直接用Derby就行.
下面是个使用derby的简单例子:
首先导入JAR包:derby.jar,如果你装的是JDK6,在C:/Program Files/Sun/JavaDB/lib目录下就可以找到.
然后就要创建数据库了:
Java代码
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是要连接数据库的名字,
create=true表示如果该数据库不存在,则创建该数据库,如果数据库存在,则用用户user=test;密码password=test连接数据库.
有了数据库,接下来该建表了:
Java代码
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();
}
创建了
USERS表,包括
ID,USER_NAME,PASSWORD三个列,其中ID是主键,其中
generated by default as identity的作用类似sequence,
identity是定义自动加一的列,
GENERATED BY ALWAYS AS IDENTITY
GENERATED BY DEFAULT AS IDENTITY
By always和by default是说明生成这个IDENTITY的方式。
By always是完全由系统自动生成。
by default是可以由用户来指定一个值。
编写与USERS表对应的javabean(这个就不多说了),:
Java代码
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;
}
}
接下来就可以就数据库进行增删改查的操作了:
插入数据:
Java代码
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代码
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方法是获得系统默认的id值,是通过identity_val_local()获得的,而函数IDENTITY_VAL_LOCAL()则可以在INSERT语句执行之后，为我们返回刚才系统为id所产生的值.感觉还是有点想sequence的curr_val.
修改数据:
Java代码
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);
}
}
}
删除数据:
Java代码
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);
}
}
}
查询数据:
Java代码
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的简单操作.
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