我正在使用Java將數據庫查詢寫入CSV文件。我該怎麼做才能循環查詢的結果,以便在CSV文件中逐行顯示。以下是我的代碼的片段。從數據庫查詢循環
StringBuilder sb = new StringBuilder();
sb.append(reportBO.projectList(this.getSearchBean());
sb,append(',');
sb.append('\n');
讓說我的查詢是
SELECT * FROM PROJECT
我正在使用Java將數據庫查詢寫入CSV文件。我該怎麼做才能循環查詢的結果,以便在CSV文件中逐行顯示。以下是我的代碼的片段。從數據庫查詢循環
StringBuilder sb = new StringBuilder();
sb.append(reportBO.projectList(this.getSearchBean());
sb,append(',');
sb.append('\n');
讓說我的查詢是
SELECT * FROM PROJECT
以下是我如何解決我的解決方案。希望它能幫助別人。感謝所有幫助..
for (int i = 0; i < ((List<BaseDTOInf>) getProjectList(searchBean)).size();i++) {
BaseDTO list = (BaseDTO) getProjectList(searchBean).get(i);
list.getDataMap().get("A");
list.getDataMap().get("B");
list.getDataMap().get("C");
list.getDataMap().get("D");
list.getDataMap().get("E");
list.getDataMap().get("F");
sb.append(list.getDataMap().get("A"));
sb.append(',');
sb.append(list.getDataMap().get("B"));
sb.append(',');
sb.append(list.getDataMap().get("C"));
sb.append(',');
sb.append(list.getDataMap().get("D"));
sb.append(',');
sb.append(list.getDataMap().get("E"));
sb.append(',');
sb.append('\n');
}
循環的結果集如下所述,並將其寫入到文件,
while (rs.next()){
sb.append(rs.getString(<ColumnName1>));
sb.append(',');
sb.append(rs.getString(<ColumnName2>));
sb.append(',');
sb.append(rs.getString(<ColumnName3>));
sb.append('\n');
}
如果你將數據填充到StringBuffer
然後確保它被寫入到在固定時間間隔的文件(例如,每1000行)。否則,如果結果包含大量行,則可能得到OutOfMemoryException
。
您需要一個CSV編寫器來正確處理這個問題。值可以包含逗號,引號,換行符,並且必須正確轉義。
從您的代碼看來,您似乎正在嘗試編寫bean,而不是直接從ResultSet中獲取東西。在這種情況下,你可以嘗試univocity-parsers:
//creates a configuration object that allows you to determine how to
//format your CSV output, among many other things. Check the tutorial.
CsvWriterSettings settings = new CsvWriterSettings();
//Configures the parser to process input objects using the BeanWriterProcessor.
//This reads the data from your java beans. In this case the type is "TestBean"
//but in yours it seems that would be something like "SearchBean".
settings.setRowWriterProcessor(new BeanWriterProcessor<TestBean>(TestBean.class));
//Defines the headers to print out to the output. My "TestBean" class has the
//following fields. Adjust this to reflect the fields in your "SearchBean"
settings.setHeaders("amount", "pending", "date", "quantity", "comments");
// Creates a CsvWriter with the settings above
CsvWriter writer = new CsvWriter(new FileWriter(new File("/path/to/file.csv")), settings);
//Loads the beans from the database.
//The "loadBeanList" method is something you should implement.
List<TestBean> beansToPersist = loadBeanList();
//With a list of beans loaded from the database, you can simply call this
//and write everything into your CSV file. You can also write beans one by one.
writer.processRecordsAndClose(beansToPersist);
披露:我是這個庫的作者。它是開放源代碼和免費的(Apache V2.0許可證)。
嗨..感謝您指出我的錯誤:)但是,你能解釋更多的解決方案,因爲我不太瞭解它。提前致謝。 @JeronimoBackes – watermelon
爲代碼添加註釋以清楚說明。 –
寫入csv文件的代碼在哪裏? –
您能否給出您從數據庫中查詢的數據示例,以及CSV文件中應該顯示的內容,它將如何顯示? –
PrintWriter pw = new PrintWriter(new File(「test.csv」)); pw.write(sb.toString()); ...這是我如何寫入CSV文件,我已經編輯了排隊 – watermelon