Java-如何在运行时动态设置字符串

Question

我必须构建一个sql查询，我必须在字符串中替换两个参数。

• 字符串变量 clean_csv_path 代表路径
• 字符串变量 lines_termination_os 代表Windows或Linux所需的Escape字符 r n，取决于。

在主执行期间，扫描仪类别提供了参数。

这是我的SQL字符串：

private static String LOAD_ALL_ALIASES = //
        "LOAD DATA LOCAL INFILE '" + CLEAN_CSV_PATH + "' INTO TABLE plantbiocore.Alias " //
                + "FIELDS TERMINATED BY ',' " //
                + "OPTIONALLY ENCLOSED BY  '"' "
                + "LINES TERMINATED BY '" + LINES_TERMINATED_OS + "'"
                + "IGNORE 1 LINES " //
                + "(locus_id, organism_id, variable, alias) "; //

 Scanner scanner = new Scanner(System.in);
 CLEAN_CSV_PATH = scanner.next() // Here the CLEAN_CSV_PATH does not appear in my LOAD_ALL_ALIASES 

Answer 1

您需要的东西称为Java中的准备序列。Google IT，有许多使用此类的示例。另一个问题是，您将其设置为" clean_csv_path"设置LOAD_ALL_ALIASES。它无法在Java中使用。

Answer 2

您需要以相反的方式做事。
首先将CLEAN_CSV_PATH与扫描仪设置。然后用。
解决您的字符串要使用不同的CLEAN_CSV_PATH创建查询，您可以将其提取到接受参数的方法中。

public void foo(){
   Scanner scanner = new Scanner(System.in);
   String csvPath = scanner.next()
   String query = getQuery(csvPath);         
   // ...
}
private static String getQuery(String csvPath){
       return "LOAD DATA LOCAL INFILE '" + csvPath + "' INTO TABLE plantbiocore.Alias " //
                + "FIELDS TERMINATED BY ',' " //
                + "OPTIONALLY ENCLOSED BY  '"' "
                + "LINES TERMINATED BY '" + LINES_TERMINATED_OS + "'"
                + "IGNORE 1 LINES " //
                + "(locus_id, organism_id, variable, alias) "; //
}

请注意，LINES_TERMINATED_OS可以用在运行时返回OS依赖行分隔符返回的System.lineSeparator()。

Answer 3

以正确的顺序写入它，然后效果很好：

    String LOAD_ALL_ALIASES;
    String CLEAN_CSV_PATH;
    String LINES_TERMINATED_OS;
    Scanner scanner = new Scanner(System.in);
    CLEAN_CSV_PATH = scanner.next();
    LINES_TERMINATED_OS = scanner.next();
    LOAD_ALL_ALIASES = "LOAD DATA LOCAL INFILE '" + CLEAN_CSV_PATH + "' INTO TABLE plantbiocore.Alias " //
            + "FIELDS TERMINATED BY ',' " //
            + "OPTIONALLY ENCLOSED BY  '"' "
            + "LINES TERMINATED BY '" + LINES_TERMINATED_OS + "'"
            + "IGNORE 1 LINES " //
            + "(locus_id, organism_id, variable, alias) ";