Java中的JTable的JDBC TableModel? [英] JDBC TableModel for a JTable in Java?

问题描述

我想将数据库表显示为JTable.我以前从未使用过JTable，所以我用Google搜索了JTable和TableModel.

I want to display a database table as a JTable. I have never used JTable before so I googled JTable and TableModel.

通过谷歌搜索，我可以编写自己的自定义TableModel来显示存储在

With that googling, I am able to write my own custom TableModel which show data stored in

Object[][] data;

现在，我想将数据库表数据显示到JTable中.我也进行了搜索，虽然对此有所了解，但仍然对AbstractTableModel的实现类中应该去的地方感到困惑.

Now, I want to show my database table data into JTable. I searched that also and have got an idea of that but still confused about what should goes where in the implementation class of AbstractTableModel.

以下是自定义TableModel的代码.

Following is the code of custom TableModel.

public abstract class AbstractPOLDATTableModel extends AbstractTableModel {
protected boolean DEBUG = false;
private String[] columnNames;
private Object[][] data;

protected AbstractPOLDATTableModel(String[] columnNames, Object[][] data) {
    this.columnNames = columnNames;
    this.data = data;
}

public int getColumnCount() {
    return columnNames.length;
}

public int getRowCount() {
    return data.length;
}

@Override
public String getColumnName(int col) {
    return columnNames[col];
}

public Object getValueAt(int row, int col) {
    return data[row][col];
}

@Override
public Class getColumnClass(int c) {
    return getValueAt(0, c).getClass();
}

@Override
public boolean isCellEditable(int row, int col) {
    if (col < 2) {
        return false;
    } else {
        return true;
    }
}

@Override
public void setValueAt(Object value, int row, int col) {
    if (DEBUG) {
        System.out.println("Setting value at " + row + "," + col
                           + " to " + value
                           + " (an instance of "
                           + value.getClass() + ")");
    }

    data[row][col] = value;
    fireTableCellUpdated(row, col);

    if (DEBUG) {
        System.out.println("New value of data:");
        printDebugData();
    }
}

private void printDebugData() {
    int numRows = getRowCount();
    int numCols = getColumnCount();

    for (int i=0; i < numRows; i++) {
        System.out.print("    row " + i + ":");
        for (int j=0; j < numCols; j++) {
            System.out.print("  " + data[i][j]);
        }
        System.out.println();
    }
    System.out.println("--------------------------");
}
}

现在，如何更改上面的代码，以便我的JTable可以具有以下功能:

Now, how to change the above code so that my JTable can have the follwing features:

1. 它显示数据库中的数据
2. 用户可以直接编辑表，当他单击保存"按钮时，更改将反映在数据库数据中
3. 用户可以直接插入数据.
4. 用户可以直接删除数据.

推荐答案

我假设您已经根据Adamski在上一个问题中提出的建议实现了1.另外，如Sanoj所建议，更改为使用某种列表来存储数据.

I'm assuming you've implemented 1 according to what Adamski suggested in your previous question. Also, as suggested by Sanoj, change to using some sort of List to store your data.

1. 要支持2-4，必须确保从数据库中提取的数据仅来自一个表，并且不包含任何派生数据(例如，聚合，column1 + column2).如果要让用户过滤行，则需要跟踪where子句.

在每一行中，存储代表用户使用GUI进行的更新的另一行(我们将其称为updatedRow).一旦对该行进行了任何更新，就需要用包含已更新数据的新行填充该字段.单击保存"后，您将使用非null的updatedRow对所有行运行更新查询，并使用updatedRow中的数据与原始行中的数据不匹配来更新数据库(如果用户将数据更改回原来的方式，则不要更新原来是).您可能还具有另一个撤消更新"按钮，该按钮将使用具有非null UpdatedRow的所有行的原始数据填充表.

我强烈建议您存储额外的元数据，在这些元数据上构成主键的字段并防止其被更改，因为对此类列的更新可能会很昂贵(因为它们可能已被索引并且可能附加了一些RI约束).应该通过使此类列不可编辑来在GUI中反映出来.更新中的where子句将仅使用这些字段，而不使用所有字段(您仍需要用户在1中设置的其他过滤器).

Within each Row, store another Row (let's call it updatedRow) that represents the updates the user has made using the GUI. Once any update is made to the row, this field needs to be populated with a new Row containing the updated data . When "Save" is clicked, you run update queries for all Rows with a non-null updatedRow, updating the database with data in updatedRow which do not match those from the original Row (don't update if the user changes data back to how it was originally). You might also have another "Undo Updates" button which populates the table with the original data for all Rows with a non-null updatedRow.

I would strongly recommend that you store additional metadata on which fields form the primary key and prevent those from being changed, as updates to such columns may be expensive (since they are presumably indexed and may have some RI constraints attached). This should be reflected in the GUI by making such columns not editable. The where clause in updates would use only these fields rather than all fields (you will still need other filters that your user set in 1).

我建议分两个步骤进行.用户通过单击向表添加一行的按钮开始.输入数据后，用户单击另一个按钮以插入数据库(或者您可以将此功能与保存"按钮中的更新结合在一起).如果主键列不是某些自动生成的ID，则需要允许新插入的行的主键字段可编辑.

要区分数据库中已存在的行和未存在的行，我建议存储一个新插入的行的列表.

如果让用户仅选择要在表中显示的某些列，则需要确定如何处理未显示的列(例如，让数据库设置默认值，并使用自动生成的ID进行填充).

I'd suggest a two step process. The user starts by clicking a button which adds a row to the table. After entering data, the user clicks another button to insert into the database (or you can combine this functionality with updates in the "save" button). You will need to allow primary key fields to be editable for newly inserted rows if the primary key columns aren't some auto-generated ID.

To different between which Rows are already in the database and which ones aren't, I'd suggest storing a list of newly inserted Rows.

If you let the user pick only certain columns to display in the table, you will need to determine how to deal with the columns that aren't being displayed (eg. let the database set a default, populate with auto-generated ID).

最好通过在每个行上都有一个复选框来实现此目的，然后单击删除"按钮，它将调用SQL以使用1中的过滤器和2中提到的主键元数据删除每个选中的行.并将其从表格中删除.

Probably best to implement this by having a checkbox with each Row, then when the "Delete" button is clicked, it calls SQL to delete each checked Row using the filter from 1 and primary key metadata mentioned in 2, as well as to remove it from the table.

一般注意事项:

• 相同的setValueAt方法将用于更新的行和插入的行，但是您需要不同的行为.您想为更新设置"updatedRow"，而不是在编辑要插入的行时设置.

• The same setValueAt method will be used for both updated and inserted Rows, but you want different behaviour. You want to set updatedRow for updates, but not when editting Rows you're about to insert.

您将如何处理错误，例如无法满足约束或输入无效(例如，数字字段中的"abcde")?

How will you handle errors such as constraints not being met or invalid input (eg. 'abcde' in a numeric field)?

SQL注入.

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