Question

我有三个主题：

    thread1:
    run() {
     while(true) {
      List<Document> documents = getDocumentsFromExternalService()
      //executes "insert into .." sql query:
      insertDocumentsToDatabase(documents)
      Thread.sleep(5000);
     }
    }

    thread2:
    run() {
     while(true) {
      //connects to database and execute "Select * from DOCS WHERE DOCS.STATE='STATE_1" query:
      List<Documents> docs = getDocumentsFromDatabaseWithState("STATE_1") 
      docsChanged = doSomethingWith(docs)
      //perform "update" SQL instruction:
      updateDocumentsInDatabase(docsChanged)
      Thread.sleep(5000);
     }
    } 

    thread3:
    run() {
     while(true) {
      //connects to database and execute "Select * from DOCS WHERE DOCS.STATE='STATE_2'" query:
      List<Documents> docs = getDocumentsFromDatabaseWithState("STATE_2") 
      docsChanged = doSomethingOtherWith(docs)
      //perform "update" SQL instruction:
      updateDocumentsInDatabase(docsChanged)
      Thread.sleep(5000);
     }
    }

所有连接都是标准的JDBC连接，并且每个线程都是独立的。问题是如何实现线程安全？这意味着 - 如何确保在执行thread2线程3的读取函数之前没有写入数据库？

Answer 1

使用数据库中的事务进行写入。

connection.setAutoCommit(false);
// do you're thing
connection.commit();
connection.setAutoCommit(true);

请参阅：http://docs.oracle.com/javase/tutorial/jdbc/basics/transactions.html

如何在Java中同步对数据库的访问？

1 个答案: