编辑建议后，代码和错误。我收到错误＆＃34; ORA-00955：名称已被现有对象使用＆＃34;现在。每次调用DataStoreManager构造函数时，序列创建都会创建此错误。
现在是代码：
public class DataStoreManager {
private Connection connection;
private PreparedStatement lookForAccount;
private PreparedStatement addAccount;
private PreparedStatement updaterBalance;
private PreparedStatement reachOperation;
public DataStoreManager(String url, String user, String password) throws DataStoreException, SQLException {
try {
connection = DriverManager.getConnection(url,user,password);
connection.setAutoCommit(false);
this.createDB();
lookForAccount = connection.prepareStatement("SELECT * FROM accounts WHERE account_id = ?");
addAccount = connection.prepareStatement("INSERT INTO accounts (account_id, balance) VALUES (? , 0.0)");
updaterBalance = connection.prepareStatement("UPDATE accounts SET balance = ? WHERE account_id = ?");
reachOperation = connection.prepareStatement("SELECT * FROM operations WHERE account_id = ? AND (date BETWEEN ? AND ?)");
} catch (SQLException error) {
error.printStackTrace();
throw error;
}
}
public void createDB() throws DataStoreException {
try {
Statement statmnt = connection.createStatement();
statmnt.executeUpdate("DROP TABLE operations");
statmnt.executeUpdate("DROP TABLE accounts");
statmnt.executeUpdate("CREATE TABLE accounts ( account_id INTEGER, balance DOUBLE PRECISION)");
statmnt.executeUpdate("CREATE TABLE operations ( operation_id INTEGER, account_id INTEGER, amount DOUBLE PRECISION, mydate DATE NOT NULL)");
//implement primary Key constraint.
statmnt.executeUpdate("ALTER TABLE accounts ADD CONSTRAINT accounts_PK PRIMARY KEY ( account_id )");
//implement foreign Key constraint
statmnt.executeUpdate("ALTER TABLE operations ADD CONSTRAINT accountID FOREIGN KEY ( account_id )"
+ "REFERENCES accounts ( account_id )");
// implement sequence for auto implement.
statmnt.executeUpdate("CREATE SEQUENCE operationID MINVALUE 1 START WITH 1 INCREMENT BY 1 CACHE 10");
statmnt.executeUpdate("CREATE SEQUENCE logID MINVALUE 1 START WITH 1 INCREMENT BY 1 CACHE 10");
// implement balance always positive constraint
statmnt.executeUpdate("ALTER TABLE accounts ADD CONSTRAINT balance_must_be_positive CHECK (balance >= 0)");
// Auto operation.
statmnt.executeUpdate("CREATE TRIGGER addingOrder BEFORE UPDATE ON accounts FOR EACH ROW BEGIN"
+ " INSERT INTO operations(operation_id, account_id, amount, mydate) "
+ " VALUES (operationID.nextval, :OLD.account_id, :NEW.amount - :OLD.amount, SYSDATE) END");
connection.commit();
} catch (Exception error) {
error.printStackTrace();
}
}
public boolean createAccount(int number) throws DataStoreException, SQLException {
try {
lookForAccount.setInt(1, number);
Boolean result = lookForAccount.execute();
if(result == true)
{
addAccount.setInt(1, number);
addAccount.executeUpdate();
connection.commit();
return true;
}
else
{ return false;}
} catch (SQLException error) {
error.printStackTrace();
throw error;
}
}
以下是我的错误：
java.sql.SQLException: ORA-00955: name is already used by an existing object
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:134)
at oracle.jdbc.ttc7.TTIoer.processError(TTIoer.java:289)
at oracle.jdbc.ttc7.Oall7.receive(Oall7.java:590)
at oracle.jdbc.ttc7.TTC7Protocol.doOall7(TTC7Protocol.java:1973)
at oracle.jdbc.ttc7.TTC7Protocol.parseExecuteFetch(TTC7Protocol.java:1119)
at oracle.jdbc.driver.OracleStatement.executeNonQuery(OracleStatement.java:2191)
at oracle.jdbc.driver.OracleStatement.doExecuteOther(OracleStatement.java:2064)
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:2989)
at oracle.jdbc.driver.OracleStatement.executeUpdate(OracleStatement.java:891)
at services.DataStoreManager.createDB(DataStoreManager.java:105)
at services.DataStoreManager.<init>(DataStoreManager.java:55)
at application.SimpleTest.main(SimpleTest.java:145)
Running single-user tests...
Running multi-users tests...
java.sql.SQLException: ORA-00955: name is already used by an existing object
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:134)
at oracle.jdbc.ttc7.TTIoer.processError(TTIoer.java:289)
at oracle.jdbc.ttc7.Oall7.receive(Oall7.java:590)
at oracle.jdbc.ttc7.TTC7Protocol.doOall7(TTC7Protocol.java:1973)
at oracle.jdbc.ttc7.TTC7Protocol.parseExecuteFetch(TTC7Protocol.java:1119)
at oracle.jdbc.driver.OracleStatement.executeNonQuery(OracleStatement.java:2191)
at oracle.jdbc.driver.OracleStatement.doExecuteOther(OracleStatement.java:2064)
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:2989)
at oracle.jdbc.driver.OracleStatement.executeUpdate(OracleStatement.java:891)
at services.DataStoreManager.createDB(DataStoreManager.java:105)
at services.DataStoreManager.<init>(DataStoreManager.java:55)
at application.SimpleTest.main(SimpleTest.java:160)
user#0[services.DataStoreManager@e00c09]: starting
user#0[services.DataStoreManager@e00c09]: exiting
java.sql.SQLException: ORA-00955: name is already used by an existing object
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:134)
at oracle.jdbc.ttc7.TTIoer.processError(TTIoer.java:289)
at oracle.jdbc.ttc7.Oall7.receive(Oall7.java:590)
at oracle.jdbc.ttc7.TTC7Protocol.doOall7(TTC7Protocol.java:1973)
at oracle.jdbc.ttc7.TTC7Protocol.parseExecuteFetch(TTC7Protocol.java:1119)
at oracle.jdbc.driver.OracleStatement.executeNonQuery(OracleStatement.java:2191)
at oracle.jdbc.driver.OracleStatement.doExecuteOther(OracleStatement.java:2064)
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:2989)
at oracle.jdbc.driver.OracleStatement.executeUpdate(OracleStatement.java:891)
at services.DataStoreManager.createDB(DataStoreManager.java:105)
at services.DataStoreManager.<init>(DataStoreManager.java:55)
at application.SimpleTest.main(SimpleTest.java:160)
user#1[services.DataStoreManager@111f9b]: starting
user#1[services.DataStoreManager@111f9b]: exiting
java.sql.SQLException: ORA-00955: name is already used by an existing object
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:134)user#2[services.DataStoreManager@1363271]: starting
user#2[services.DataStoreManager@1363271]: exiting
at oracle.jdbc.ttc7.TTIoer.processError(TTIoer.java:289)
at oracle.jdbc.ttc7.Oall7.receive(Oall7.java:590)
at oracle.jdbc.ttc7.TTC7Protocol.doOall7(TTC7Protocol.java:1973)
at oracle.jdbc.ttc7.TTC7Protocol.parseExecuteFetch(TTC7Protocol.java:1119)
at oracle.jdbc.driver.OracleStatement.executeNonQuery(OracleStatement.java:2191)
at oracle.jdbc.driver.OracleStatement.doExecuteOther(OracleStatement.java:2064)
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:2989)
at oracle.jdbc.driver.OracleStatement.executeUpdate(OracleStatement.java:891)
at services.DataStoreManager.createDB(DataStoreManager.java:105)
at services.DataStoreManager.<init>(DataStoreManager.java:55)
at application.SimpleTest.main(SimpleTest.java:160)
java.sql.SQLException: ORA-00955: name is already used by an existing object
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:134)
at oracle.jdbc.ttc7.TTIoer.processError(TTIoer.java:289)
at oracle.jdbc.ttc7.Oall7.receive(Oall7.java:590)
at oracle.jdbc.ttc7.TTC7Protocol.doOall7(TTC7Protocol.java:1973)
at oracle.jdbc.ttc7.TTC7Protocol.parseExecuteFetch(TTC7Protocol.java:1119)
at oracle.jdbc.driver.OracleStatement.executeNonQuery(OracleStatement.java:2191)
at oracle.jdbc.driver.OracleStatement.doExecuteOther(OracleStatement.java:2064)
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:2989)
at oracle.jdbc.driver.OracleStatement.executeUpdate(OracleStatement.java:891)
at services.DataStoreManager.createDB(DataStoreManager.java:105)
at services.DataStoreManager.<init>(DataStoreManager.java:55)
at application.SimpleTest.main(SimpleTest.java:160)
user#3[services.DataStoreManager@114f313]: starting
user#3[services.DataStoreManager@114f313]: exiting
java.sql.SQLException: ORA-00955: name is already used by an existing object
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:134)user#4[services.DataStoreManager@d767dc]: starting
user#4[services.DataStoreManager@d767dc]: exiting
at oracle.jdbc.ttc7.TTIoer.processError(TTIoer.java:289)
at oracle.jdbc.ttc7.Oall7.receive(Oall7.java:590)
at oracle.jdbc.ttc7.TTC7Protocol.doOall7(TTC7Protocol.java:1973)
at oracle.jdbc.ttc7.TTC7Protocol.parseExecuteFetch(TTC7Protocol.java:1119)
at oracle.jdbc.driver.OracleStatement.executeNonQuery(OracleStatement.java:2191)
at oracle.jdbc.driver.OracleStatement.doExecuteOther(OracleStatement.java:2064)
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:2989)
at oracle.jdbc.driver.OracleStatement.executeUpdate(OracleStatement.java:891)
at services.DataStoreManager.createDB(DataStoreManager.java:105)
at services.DataStoreManager.<init>(DataStoreManager.java:55)
at application.SimpleTest.main(SimpleTest.java:160)
答案 0 :(得分：1)
如果您的任何SQL语句生成错误（例如，如果表不存在且您尝试删除它），则createDB()方法会出现问题。此时，您的代码将跳转到catch块，并且不会创建任何数据库对象。您需要将每个DROP语句包装在try / catch块中，以便可以捕获和处理任何错误（或者在您的情况下可以安全地忽略）然后运行CREATE语句。
您还只为表格运行DROP语句。您需要对序列和触发器执行相同的操作。
您的触发器也无效。帐户表仅包含account_id和balance的列。您无法为操作表中的列引用:old或:new值。因此:old.amount和:new.amount无效，而:old.account_id是来自帐户表格的account_id（结果与account_id中的operations相同表，因为它是一个外键）。你也错过了两个分号。它应该是这样的：
statmnt.executeUpdate("CREATE TRIGGER addingOrder BEFORE UPDATE ON accounts FOR EACH ROW BEGIN"
+ " INSERT INTO operations(... columns ...) "
+ " VALUES (... values ...); END;");
你编写事物的方式，你试图先通过DROPPING所有内容进行一些清理，然后你CREATE一切。测试完成后，您将留下所有数据库对象。我建议你颠倒你的订单，以便在测试开始时创建你的对象，然后在你DROP所有内容的末尾进行拆除，以便数据库保持干净。