JDBC异常处理:警告抑制 [英] JDBC exception handling: warning suppression

问题描述

我目前正在学习一些基本的Java SQL编码，为我的SQL项目制作了一个基本的终端UI.我一直在使用PostgreSQL

I am currently learning some basic java SQL coding, making a basic terminal UI for my SQL project. I have been using PostgreSQL

我正在使用PreparedStatement来确保自己免受SQL注入的伤害，总比后悔要安全. PreparedStatement似乎总是出于某种原因发出警告，我认为这是异常的子类(应该被异常捕获).

I am using PreparedStatement to ensure myself from SQL injections, better be safe than sorry. PreparedStatement seems to always fire warnings for some reason, which I figured is a subclass to exceptions (and should get caught in the exceptions).

在我的SQL触发器和函数中，我创建并测试了我应该触发异常的情况，这些异常都可以正常工作并捕获catch块.

In my SQL triggers and functions I have created and tested the cases where I should fire exceptions, and they are all getting and working properly catch block.

我猜想使用@Supresswarnings让编译器知道我想抑制我的警告，但是我可能想在catch块中捕捉一些警告，所以我可能正在寻找其他解决方案.

I guess using @Supresswarnings to let the compiler know I want to do suppress my warnings, but I might want to catch some warnings in the catch block, so I might be looking for a different solution.

问题/问题是:

1. 我想将我的照片放在try块中，这没有引发异常.
2. 在try块中执行preparedStmt.executeQuery后，如何进行打印?
3. 在处理这样的异常处理时，通常使用@SuppressWarnings被认为是良好的编码习惯吗?
4. 如果我对preparedStatement.executeQuery()总是发出警告不正确，那么SQL语言中的警告被视为什么?

1. I would like to have my prints in the try block, that is no exceptions were fired.
2. What could be done to have my prints after the execution of preparedStmt.executeQuery in the try block?
3. Is using @SuppressWarnings usually considered good coding practice when dealing with exception handling like this?
4. If I am incorrect about preparedStatement.executeQuery() always fires warnings, what is considered warnings in SQL language?

我的代码:

void registerStudent(Connection conn, String toBeInserted, String insertedTo)
throws SQLException{
    ResultSet res;
    String query = "INSERT INTO Registrations VALUES (?, ?)";

    PreparedStatement ps = conn.prepareStatement(query);
    ps.setString(1, toBeInserted);
    ps.setString(2, insertedTo);

    try {
        ps.executeQuery();                        

    }catch (SQLException e) {

        SQLWarning warning = ps.getWarnings();
        if (warning != null){

        System.out.println("Yay,  insert succeeded!
    values: "+ toBeInserted +" were inserted into 
    "+insertedTo);

        }else {
            System.out.println("Nothing inserted, here goes the big exception SQL fired for ya'll: " 
         + e.getMessage());
        }
    }
  }

推荐答案

仍然存在一些缺陷.我还添加了AUTOINCREMENT主键的情况-您可以在插入 后检索它.

There are still some flaws. I added also the case of an AUTOINCREMENT primary key - which you can retrieve after inserting.

缺陷:

• 列出您要插入的字段，这样以后在数据库中添加一列就不会引起问题，并且在代码中列的顺序也很清楚.
• 使用try-with-resources关闭语句，结果集等，即使其中一个返回或抛出异常也是如此.
• 将executeUpdate用于INSERT(和类似的修改操作)，以返回更新计数.
• 您捕获了SQLException，然后应重新抛出该SQLException，以使调用方确定在严重失败时应采取的措施.
• SQLWarnings(实际的SQL和SQLException也是如此)可能很有趣， 尽管我并不经常看到SQLWarnings被治疗.对于这种简单的情况，也许会忘记它，而是先在单独的SQL工具中尝试新的SQL语句.

• List which fields you insert, such that a later addition of a column in the database does not cause problems, and the order of columns is clear in the code.
• Use try-with-resources to close statement, result set and such, even when one returns inside, or an exception is thrown.
• Use executeUpdate for INSERT (and similar modifying operations) returning an update count.
• You catched the SQLException, which then should be rethrown, to let the caller determine what to do on gross failure.
• SQLWarnings (as does the actual SQL and the SQLException) might be interesting, though I not often see SQLWarnings being treated. Maybe forget it for such simple case, and instead try new SQL statements first in a separate SQL tool.

所以:

/**
 * @return the generated primary key, the Student ID.
 */
int registerStudent(Connection conn, String toBeInserted, String insertedTo)
        throws SQLException {
    String query = "INSERT INTO Registrations(ToBeInserted, InsertedInto) VALUES(?, ?)";

    try (PreparedStatement ps = conn.prepareStatement(query),
            Statement.RETURN_GENERATED_KEYS) {
        ps.setString(1, toBeInserted);
        ps.setString(2, insertedTo);
        int updateCount = ps.executeUpdate();                        
        if (updateCount == 1) {
            try (ResultSet rs = ps.getGeneratedKeys()) {
                if (rs.next()) {
                    int id = rs.getInt(1);
                    return id;
                }
            }
            throw new SQLException("No primary key generated");
        } else {
            SQLWarning warning = ps.getWarnings();
            Logger.getLogger(Xyz.class.getName()).info("Not added, values: "
                + toBeInserted + " were not inserted into "+ insertedTo + ": " + warning);
            throw new SQLException("Not added");
        }
    }
}

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