Exemple de transaction JDBC

La transaction JDBC garantit qu'un ensemble d'instructions SQL est exécuté en tant qu'unité, soit toutes les instructions sont exécutées avec succès, soit AUCUNE des instructions n'est exécutée (annulation de toutes les modifications).

1. Sans transaction JDBC

1.1 A JDBC example to insert two rows and update one row.

TransactionExample.java

package com.example.jdbc;

import java.math.BigDecimal;
import java.sql.*;
import java.time.LocalDateTime;

public class TransactionExample {

    public static void main(String[] args) {

        try (Connection conn = DriverManager.getConnection(
                "jdbc:postgresql://127.0.0.1:5432/test", "postgres", "password");
             Statement statement = conn.createStatement();
             PreparedStatement psInsert = conn.prepareStatement(SQL_INSERT);
             PreparedStatement psUpdate = conn.prepareStatement(SQL_UPDATE)) {

            statement.execute(SQL_TABLE_DROP);
            statement.execute(SQL_TABLE_CREATE);

            // Run list of insert commands
            psInsert.setString(1, "example");
            psInsert.setBigDecimal(2, new BigDecimal(10));
            psInsert.setTimestamp(3, Timestamp.valueOf(LocalDateTime.now()));
            psInsert.execute();

            psInsert.setString(1, "kungfu");
            psInsert.setBigDecimal(2, new BigDecimal(20));
            psInsert.setTimestamp(3, Timestamp.valueOf(LocalDateTime.now()));
            psInsert.execute();

            // Run list of update commands

            // below line caused error, test transaction
            // org.postgresql.util.PSQLException: No value specified for parameter 1.
            psUpdate.setBigDecimal(2, new BigDecimal(999.99));

            //psUpdate.setBigDecimal(1, new BigDecimal(999.99));
            psUpdate.setString(2, "example");
            psUpdate.execute();

        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    private static final String SQL_INSERT = "INSERT INTO EMPLOYEE (NAME, SALARY, CREATED_DATE) VALUES (?,?,?)";

    private static final String SQL_UPDATE = "UPDATE EMPLOYEE SET SALARY=? WHERE NAME=?";

    private static final String SQL_TABLE_CREATE = "CREATE TABLE EMPLOYEE"
            + "("
            + " ID serial,"
            + " NAME varchar(100) NOT NULL,"
            + " SALARY numeric(15, 2) NOT NULL,"
            + " CREATED_DATE timestamp with time zone NOT NULL DEFAULT CURRENT_TIMESTAMP,"
            + " PRIMARY KEY (ID)"
            + ")";

    private static final String SQL_TABLE_DROP = "DROP TABLE EMPLOYEE";

}

Sortie, la mise à jour a échoué et levant une exception, à la fin, 2 lignes sont insérées mais la mise à jour est ignorée.

org.postgresql.util.PSQLException: No value specified for parameter 1.
    at org.postgresql.core.v3.SimpleParameterList.checkAllParametersSet(SimpleParameterList.java:257)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:292)
    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:441)
    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:365)
    at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:143)
    at org.postgresql.jdbc.PgPreparedStatement.execute(PgPreparedStatement.java:132)
    at com.example.jdbc.TransactionExample.main(TransactionExample.java:41)

output

2. Utilisation de la transaction JDBC

2.1 To enable transaction, set auto commit to false.

conn.setAutoCommit(false); // default true
// start transaction block

// insert
// update
// if any errors within the start and end block,
// rolled back all changes, none of the statements are executed.

// end transaction block
conn.commit();

2.2 Same example with JDBC transaction.

TransactionExample.java

package com.example.jdbc;

import java.math.BigDecimal;
import java.sql.*;
import java.time.LocalDateTime;

public class TransactionExample {

    public static void main(String[] args) {

        try (Connection conn = DriverManager.getConnection(
                "jdbc:postgresql://127.0.0.1:5432/test", "postgres", "password");
             Statement statement = conn.createStatement();
             PreparedStatement psInsert = conn.prepareStatement(SQL_INSERT);
             PreparedStatement psUpdate = conn.prepareStatement(SQL_UPDATE)) {

            statement.execute(SQL_TABLE_DROP);
            statement.execute(SQL_TABLE_CREATE);

            // start transaction block
            conn.setAutoCommit(false); // default true

            // Run list of insert commands
            psInsert.setString(1, "example");
            psInsert.setBigDecimal(2, new BigDecimal(10));
            psInsert.setTimestamp(3, Timestamp.valueOf(LocalDateTime.now()));
            psInsert.execute();

            psInsert.setString(1, "kungfu");
            psInsert.setBigDecimal(2, new BigDecimal(20));
            psInsert.setTimestamp(3, Timestamp.valueOf(LocalDateTime.now()));
            psInsert.execute();

            // Run list of update commands

            // error, test roolback
            // org.postgresql.util.PSQLException: No value specified for parameter 1.
            psUpdate.setBigDecimal(2, new BigDecimal(999.99));
            //psUpdate.setBigDecimal(1, new BigDecimal(999.99));
            psUpdate.setString(2, "example");
            psUpdate.execute();

            // end transaction block, commit changes
            conn.commit();

            // good practice to set it back to default true
            conn.setAutoCommit(true);

        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    //...

}

Sortie, aucune des instructions n'est exécutée, les instructions d'insertion sont annulées.

org.postgresql.util.PSQLException: No value specified for parameter 1.
    at org.postgresql.core.v3.SimpleParameterList.checkAllParametersSet(SimpleParameterList.java:257)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:292)
    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:441)
    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:365)
    at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:143)
    at org.postgresql.jdbc.PgPreparedStatement.execute(PgPreparedStatement.java:132)
    at com.example.jdbc.TransactionExample.main(TransactionExample.java:41)

output

3. Supplémentaire…

Corrigez l'erreurparameter 1 et voyez le résultat attendu.

    //psUpdate.setBigDecimal(2, new BigDecimal(999.99));

    psUpdate.setBigDecimal(1, new BigDecimal(999.99));
    psUpdate.setString(2, "example");
    psUpdate.execute();

Sortie

2 rows are inserted and 1 row is updated.

output

Télécharger le code source

$ git clone https://github.com/example/java-jdbc.git
$ cd postgresql

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Exemple de transaction JDBC