System.out.printf("属性:%-10s ", rsmd.getColumnName(i));
System.out.printf("类型:%-10s\n", rsmd.getColumnTypeName(i));

System.out.printf("属性:%10s ", rsmd.getColumnName(i));
System.out.printf("类型:%10s\n", rsmd.getColumnTypeName(i));

package tools;

import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Iterator;

/**
 * 结果集打印机.将结果集中的数据打印成表格.
 */
public class ResultSetPrinter {
    public static void printResultSet(ResultSet rs) throws SQLException {
        ResultSetMetaData resultSetMetaData = rs.getMetaData();
        // 获取列数
        int ColumnCount = resultSetMetaData.getColumnCount();
        // 保存当前列最大长度的数组
        int[] columnMaxLengths = new int[ColumnCount];
        // 缓存结果集,结果集可能有序,所以用ArrayList保存变得打乱顺序.
        ArrayList<String[]> results = new ArrayList<>();
        // 按行遍历
        while (rs.next()) {
            // 保存当前行所有列
            String[] columnStr = new String[ColumnCount];
            // 获取属性值.
            for (int i = 0; i < ColumnCount; i++) {
                // 获取一列
                columnStr[i] = rs.getString(i + 1);
                // 计算当前列的最大长度
                columnMaxLengths[i] = Math.max(columnMaxLengths[i], (columnStr[i] == null) ? 0 : columnStr[i].length());
            }
            // 缓存这一行.
            results.add(columnStr);
        }
        printSeparator(columnMaxLengths);
        printColumnName(resultSetMetaData, columnMaxLengths);
        printSeparator(columnMaxLengths);
        // 遍历集合输出结果
        Iterator<String[]> iterator = results.iterator();
        String[] columnStr;
        while (iterator.hasNext()) {
            columnStr = iterator.next();
            for (int i = 0; i < ColumnCount; i++) {
                // System.out.printf("|%" + (columnMaxLengths[i] + 1) + "s", columnStr[i]);
                System.out.printf("|%" + columnMaxLengths[i] + "s", columnStr[i]);
            }
            System.out.println("|");
        }
        printSeparator(columnMaxLengths);
    }

    /**
     * 输出列名.
     *
     * @param resultSetMetaData 结果集的元数据对象.
     * @param columnMaxLengths  每一列最大长度的字符串的长度.
     * @throws SQLException
     */
    private static void printColumnName(ResultSetMetaData resultSetMetaData, int[] columnMaxLengths) throws SQLException {
        int columnCount = resultSetMetaData.getColumnCount();
        for (int i = 0; i < columnCount; i++) {
            // System.out.printf("|%" + (columnMaxLengths[i] + 1) + "s", resultSetMetaData.getColumnName(i + 1));
            System.out.printf("|%" + columnMaxLengths[i] + "s", resultSetMetaData.getColumnName(i + 1));
        }
        System.out.println("|");
    }

    /**
     * 输出分隔符.
     *
     * @param columnMaxLengths 保存结果集中每一列的最长的字符串的长度.
     */
    private static void printSeparator(int[] columnMaxLengths) {
        for (int i = 0; i < columnMaxLengths.length; i++) {
            System.out.print("+");
            // for (int j = 0; j < columnMaxLengths[i] + 1; j++) {
            for (int j = 0; j < columnMaxLengths[i]; j++) {
                System.out.print("-");
            }
        }
        System.out.println("+");
    }

}

package tools;
import java.sql.*;

public class Test {
    private static String driver = "com.mysql.cj.jdbc.Driver";
    private static String URL = "jdbc:mysql://127.0.0.1:3306/university?serverTimezone=UTC";
    private static String user = "root";
    private static String password = "root";

    /**
     * JDBC测试.
     */
    private static void JDBCexample() {
        // 1.加载数据库驱动
        try {

            Class.forName(driver);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        testStatement();
    }

    /**
     * 测试Statement的用法.
     */
    private static void testStatement() {
        try (// 2.打开数据库连接
             Connection conn = DriverManager.getConnection(URL, user, password);
             // 3.创建语句
             Statement stmt = conn.createStatement()) {
            // 模拟SQL注入
            testSqlInjecton(stmt);

        } catch (SQLException sqle) {
            System.out.println("SQLException : " + sqle);
        }
    }

    /**
     * 模拟SQL注入.
     *
     * @param stmt Statement对象.
     * @throws SQLException
     */
    private static void testSqlInjecton(Statement stmt) throws SQLException {
        String name = "X' or 'Y' = 'Y";
        String sql = "select * from instructor where name = '" + name + "'";
        ResultSet rs = stmt.executeQuery(sql);
        ResultSetPrinter.printResultSet(rs);
    }

    public static void main(String[] args) {
        JDBCexample();
    }
}

sb.append("<property name=\"" + group1 + "\" value=\"${" + group1+ "}\"/>\r\n");

sb.append("<property name=\"" + group1 + "\" value=\"${" + group1+ "}\"/>\r\n");

sb.append("<property name=\"").append(group1).append("\" value=\"${").append(group1).append("}\"/>\r\n");

/**
 * 把StringBuffer或StringBuilder中的字符串连接符<code>+</code>替换append()方法
 *
 * @return 替换后的字符串.
 */
public String StringConnectorToAppend(String stringBufferAppendCode) {
    String returnValue = "// " + stringBufferAppendCode + "\n";
    return returnValue + stringBufferAppendCode.replaceAll("\\s*\\+\\s*", ").append(");
}