DBUtils

结果集常用类实现

List为空的类返回值是[]、没有List的类为空返回值是null

sql = "select * from category";
// ArrayHandle
// 只获取首行数据
Arrays.toString(queryRunner.query(sql, new ArrayHandler()));
// ArrayListHander
// 获取多行数据
List<Object[]> query = queryRunner.query(sql, new ArrayListHandler());
for(Object[] objs: query){
  System.out.println("category_id：" + objs[0]);
  System.out.println("category_name：" + objs[1]);
}
// BeanHandler
// 获取一个对象
Category query = queryRunner.query(sql, new BeanHandler<>(Category.class));
System.out.println(query.getCategory_id());
System.out.println(query.getCategory_name());
// BeanListHandler
// 获取对象数组
List<Category> query = queryRunner.query(sql, new BeanListHandler<>(Category.class));
for(Category cat: query){
  System.out.println(cat.getCategory_id() +"——"+ cat.getCategory_name());
}
// MapHandler
// 获取一个map字典
Map<String, Object> query = queryRunner.query(sql, new MapHandler());
System.out.println(query.getOrDefault("category_id", "0"));
System.out.println(query.getOrDefault("category_name", "null"));
// MapListHandler
List<Map<String, Object>> query = queryRunner.query(sql, new MapListHandler());
for(Map map: query){
  System.out.println(map.getOrDefault("category_id", "0") +"——"+
    map.getOrDefault("category_name", "null"));
}

数据库操作函数

queryRunner.update(sql);
  int update("insert into table value(...)");    // 增
  int update("delete from table where id=1");    // 删
  int update("update table set id=2 where id=1");//改
queryRunner.query(sql, rsh);
  ResultSetHandler query("select * from table", new ResultSetHandler());

基本用法

初始化线程池

public class PoolUtils {
  private static DataSource dataSource = null;
  static {
    //完成连接池的初始化
    InputStream ips = PoolUtils.class.getClassLoader().getResourceAsStream("druid.properties");
    Properties properties = new Properties();
    try {
      properties.load(ips);
    } catch (IOException e) {
      e.printStackTrace();
    }
    try {
      dataSource = (DruidDataSource) DruidDataSourceFactory.createDataSource(properties);
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
  /**
  * 对外提供连接！
  */
  public static DataSource getDataSource() {
    return dataSource;
  }
  /**
  * 对外提供获取连接的方法！
  */
  public static Connection getConnection() throws SQLException {
    //使用连接池获取连接返回
    return dataSource.getConnection();
  }
}

public class test{
  private static QueryRunner queryRunner = new QueryRunner(PoolUtils.getDataSource());
  private static String sql = "select * from category";
  public static void main(String[] args) throw SQLException {
    System.out.println(Arrays.toString(queryRunner.query(sql, new ArrayHandler())));
  }
}