将参数动态设置为JDBC中准备好的Statement

Question

我有一个所有DAO的公共类,我们将读取查询并执行它们,如下所示.我将从DAO发送参数到这个类.

Connection connection = Queries.getConnection();
String query = Queries.getQuery(queryName);//Queries i will get from xml
PreparedStatement preparedStatement =  connection.prepareStatement(query);

什么是动态设置参数到JDBC中准备好的Statement的最佳方法.我相信,我们在JDBC中没有像JDBC中那样的命名参数概念.在我们的项目中,我们只是简单的JDBC.

Answer 1

写这样的东西：

public static int mapParams(PreparedStatement ps, Object... args) throws SQLException {
    int i = 1;
    for (Object arg : args) {         
         if (arg instanceof Date) {
        ps.setTimestamp(i++, new Timestamp(((Date) arg).getTime()));
    } else if (arg instanceof Integer) {
        ps.setInt(i++, (Integer) arg);
    } else if (arg instanceof Long) {
        ps.setLong(i++, (Long) arg);
    } else if (arg instanceof Double) {
        ps.setDouble(i++, (Double) arg);
    } else if (arg instanceof Float) {
        ps.setFloat(i++, (Float) arg);
    } else {
        ps.setString(i++, (String) arg);
    }
   }
  }
}

并且在查询中只使用 '?' 您需要在哪里设置参数。

我知道这是老式的代码，但只是举一些简约的例子......

Answer 2

好方法是使用Map

Map<String, Object> params = new HashMap<>();
params.put("id",0);
params.put("name","test");
//more params here...


String sql = "SELECT * FROM test";

boolean first = true;

for (String paramName : params.keySet()) {
    Object paramValue = params.get(paramName);
    if (paramValue != null) {
        if (first){
            sql += " where " + paramName + "=?";
            first = false;
        } else {
            sql += " and " + paramName + "=?";
        }
    }
}

Connection connection = DataSource.getInstance().getConnection();

ps = connection.prepareStatement(sql);

int paramNumber = 1;
for (String paramName : params.keySet()) {
    Object paramValue = params.get(paramName);
    if (paramValue != null) {
        if (param instanceof Date) {
            ps.setDate(paramNumber, (Date) param);
        } else if (param instanceof Integer) {
            ps.setInt(paramNumber, (Integer) param);
        //more types here...
        } else {
            ps.setString(paramNumber, param.toString());
        }
        paramNumber ++;
    }
}

Answer 3

看看这个页面的例子。您的查询应包含 ? 在您想要设置值的地方。

String query = "update COFFEES set SALES = ? where COF_NAME = ?";

你可以轻松地设置这样的值

preparedStatement.setInt(1, 100);
preparedStatement.setString(2, "French_Roast");