Java Reference
In-Depth Information
Example 17−1: ExecuteSQL.java (continued)
* textual table. It relies on the ResultSetMetaData class, but a fair
* bit of the code is simple string manipulation.
**/
static void printResultsTable(ResultSet rs, OutputStream output)
throws SQLException
{
// Set up the output stream
PrintWriter out = new PrintWriter(output);
// Get some "meta data" (column names, etc.) about the results
ResultSetMetaData metadata = rs.getMetaData();
// Variables to hold important data about the table to be displayed
int numcols = metadata.getColumnCount(); // how many columns
String[] labels = new String[numcols];
// the column labels
int[] colwidths = new int[numcols];
// the width of each
int[] colpos = new int[numcols];
// start position of each
int linewidth;
// total width of table
// Figure out how wide the columns are, where each one begins,
// how wide each row of the table will be, etc.
linewidth = 1; // for the initial '|'.
for(int i = 0; i < numcols; i++) { // for each column
colpos[i] = linewidth; // save its position
labels[i] = metadata.getColumnLabel(i+1); // get its label
// Get the column width. If the db doesn't report one, guess
// 30 characters. Then check the length of the label, and use
// it if it is larger than the column width
int size = metadata.getColumnDisplaySize(i+1);
if (size == -1) size = 30; // Some drivers return -1...
if (size > 500) size = 30; // Don't allow unreasonable sizes
int labelsize = labels[i].length();
if (labelsize > size) size = labelsize;
colwidths[i] = size + 1;
// save the column the size
linewidth += colwidths[i] + 2;
// increment total size
}
// Create a horizontal divider line we use in the table.
// Also create a blank line that is the initial value of each
// line of the table
StringBuffer divider = new StringBuffer(linewidth);
StringBuffer blankline = new StringBuffer(linewidth);
for(int i = 0; i < linewidth; i++) {
divider.insert(i, '-');
blankline.insert(i, " ");
}
// Put special marks in the divider line at the column positions
for(int i=0; i<numcols; i++) divider.setCharAt(colpos[i]-1,'+');
divider.setCharAt(linewidth-1, '+');
// Begin the table output with a divider line
out.println(divider);
// The next line of the table contains the column labels.
// Begin with a blank line, and put the column names and column
// divider characters "|" into it. overwrite() is defined below.
StringBuffer line = new StringBuffer(blankline.toString());
line.setCharAt(0, '|');
