java如何使用JDBC从存储过程中获取*everything*

# 1 楼答案

当我们在JDBC中执行一个存储过程时，我们会返回一系列零或更多的“结果”。然后我们可以通过调用CallableStatement#getMoreResults()顺序处理这些“结果”。每个“结果”可以包含

我们可以使用ResultSet对象检索的零行或多行数据
DML语句（INSERT、update、DELETE）的更新计数，我们可以使用CallableStatement#getUpdateCount()检索，或者
引发SQLServerException的错误

对于“问题1”，问题通常是存储过程不是以SET NOCOUNT ON;开头，而是在执行SELECT以生成结果集之前执行DML语句。DML的更新计数作为第一个“结果”返回，数据行“卡在后面”，直到我们调用getMoreResults

“问题2”本质上是同一个问题。在错误发生之前，存储过程会生成一个“结果”（通常是SELECT，也可能是update count）。该错误会在后续的“结果”中返回，并且不会导致异常，直到我们使用getMoreResults来“检索”它

在许多情况下，只需在存储过程中添加SET NOCOUNT ON;作为第一个可执行语句，就可以避免这个问题。然而，对存储过程的更改并不总是可能的，事实仍然是，为了从存储过程中获取所有信息，我们需要继续调用^{，直到，正如Javadoc所说：

There are no more results when the following is true: 

     // stmt is a Statement object
     ((stmt.getMoreResults() == false) && (stmt.getUpdateCount() == -1))

这听起来很简单，但像往常一样，“魔鬼在细节中”，如下例所示。对于SQL Server存储过程

ALTER PROCEDURE dbo.TroublesomeSP AS
BEGIN
      note: no `SET NOCOUNT ON;`
    DECLARE @tbl TABLE (id VARCHAR(3) PRIMARY KEY);

    DROP TABLE NonExistent;
    INSERT INTO @tbl (id) VALUES ('001');
    SELECT id FROM @tbl;
    INSERT INTO @tbl (id) VALUES ('001');    duplicate key error
    SELECT 1/0;    error _inside_ ResultSet
    INSERT INTO @tbl (id) VALUES ('101');
    INSERT INTO @tbl (id) VALUES ('201'),('202');
    SELECT id FROM @tbl;
END

。。。下面的Java代码将返回所有内容

try (CallableStatement cs = conn.prepareCall("{call dbo.TroublesomeSP}")) {
    boolean resultSetAvailable = false;
    int numberOfResultsProcessed = 0;
    try {
        resultSetAvailable = cs.execute();
    } catch (SQLServerException sse) {
        System.out.printf("Exception thrown on execute: %s%n%n", sse.getMessage());
        numberOfResultsProcessed++;
    }
    int updateCount = -2;  // initialize to impossible(?) value
    while (true) {
        boolean exceptionOccurred = true; 
        do {
            try {
                if (numberOfResultsProcessed > 0) {
                    resultSetAvailable = cs.getMoreResults();
                }
                exceptionOccurred = false;
                updateCount = cs.getUpdateCount();
            } catch (SQLServerException sse) {
                System.out.printf("Current result is an exception: %s%n%n", sse.getMessage());
            }
            numberOfResultsProcessed++;
        } while (exceptionOccurred);

        if ((!resultSetAvailable) && (updateCount == -1)) {
            break;  // we're done
        }

        if (resultSetAvailable) {
            System.out.println("Current result is a ResultSet:");
            try (ResultSet rs = cs.getResultSet()) {
                try {
                    while (rs.next()) {
                        System.out.println(rs.getString(1));
                    }
                } catch (SQLServerException sse) {
                    System.out.printf("Exception while processing ResultSet: %s%n", sse.getMessage());
                }
            }
        } else {
            System.out.printf("Current result is an update count: %d %s affected%n",
                    updateCount,
                    updateCount == 1 ? "row was" : "rows were");
        }
        System.out.println();
    }
    System.out.println("[end of results]");
}

。。。生成以下控制台输出：

Exception thrown on execute: Cannot drop the table 'NonExistent', because it does not exist or you do not have permission.

Current result is an update count: 1 row was affected

Current result is a ResultSet:
001

Current result is an exception: Violation of PRIMARY KEY constraint 'PK__#314D4EA__3213E83F3335971A'. Cannot insert duplicate key in object 'dbo.@tbl'. The duplicate key value is (001).

Current result is a ResultSet:
Exception while processing ResultSet: Divide by zero error encountered.

Current result is an update count: 1 row was affected

Current result is an update count: 2 rows were affected

Current result is a ResultSet:
001
101
201
202

[end of results]

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java如何使用JDBC从存储过程中获取everything

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