Java-JDBC-JDBCUtils工具类

Java-JDBC-JDBCUtils工具类

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目录

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内容

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  之前关于JDBC的测试，都有一些相同的步骤：

1. 数据库连接
2. 资源释放

每次都要书写相同的步骤，是不是很麻烦？那么我们就可以编写个工具类，把这些共同的操作放一起，方便以后使用。

• 工具类代码分析：

  • 需要一个获取连接对象的方法getConnection
    • getConnection所需参数url, username, password通过配置文件获取
    • 只需要读取一次，可以在静态代码块中配置
  • 需要释放资源的方法close

• 工具类代码：

    package cn.gaogzhen.util;
  
    import java.io.IOException;
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    import java.util.Properties;
  
    public class JDBCUtils {
    	private static Connection conn;
    	/**
    	 * 静态代码块，获取配置信息
    	 */
    	static {
  
    		try {
    			Properties prop = new Properties();
    			prop.load(JDBCUtils.class.getClassLoader().getResourceAsStream("jdbc.properties"));
    			String url = prop.getProperty("url");
    			String username = prop.getProperty("username");
    			String password = prop.getProperty("password");
    			String driver = prop.getProperty("driver");
    			// 注册驱动
    			Class.forName(driver);
    			conn = DriverManager.getConnection(url, username, password);
  
    		} catch (IOException | ClassNotFoundException | SQLException e) {
    			e.printStackTrace();
    		} 
    	}
  
    	public static Connection getConnection() throws SQLException {
    		return conn;
    	}
  
    	/**
    	 * 释放资源
    	 * @param rs 	结果集对象
    	 * @param stmt	执行SQL语句对象
    	 * @param conn	连接对象
    	 */
    	public static void close(ResultSet rs, Statement stmt, Connection conn) {
    		if(rs != null) {
    			try {
    				rs.close();
    			} catch (SQLException e) {
    				e.printStackTrace();
    			}
    		}
  
    		if(stmt != null) {
    			try {
    				stmt.close();
    			} catch (SQLException e) {
    				e.printStackTrace();
    			}
    		}
  
    		if(conn != null) {
    			try {
    				conn.close();
    			} catch (SQLException e) {
    				e.printStackTrace();
    			}
    		}
    	}
  
    	public static void close(Statement stmt, Connection conn) {
    		close(null, stmt, conn);
    	}
    }
  

• 使用测试：获取表emp中所有数据，封装对象并放入集合中-改造

    // 之前没用工具类代码在JDBC快速入门博文中
    // 改造后
    package cn.gaogzhen.jdbc;
  
    import java.sql.Connection;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
  
    import cn.gaogzhen.domain.Emp;
    import cn.gaogzhen.util.JDBCUtils;
  
    public class JDBCDemo6 {
    	public static void main(String[] args) {
    		List<Emp> list = new JDBCDemo6().findAll();
    		System.out.println(list);
    	 }
  
    	public List<Emp> findAll() {
    		Connection conn = null;
    		Statement stmt = null;
    		ResultSet rs = null;
    		List<Emp> list = new ArrayList<>();
    		 // 2. 注册驱动
    		try {
  
    		   conn = JDBCUtils.getConnection();
    			// 4. sql语句
    			String sql = "select * from emp";
    			// 5. 获取执行sql语句的对象statement
    			stmt = conn.createStatement();
    			// 6. 执行sql操作,获取结果
    			rs = stmt.executeQuery(sql);
    			// 7. 解析结果
  
    			while(rs.next()) {
    			   int id = rs.getInt("id");
    			   String ename = rs.getString("ename");
    			   int job_id = rs.getInt("job_id");
    			   int mgr = rs.getInt("mgr");
    			   Date joindate = rs.getDate("joindate");
    			   double salary = rs.getDouble("salary");
    			   double bonus = rs.getDouble("bonus");
    			   int dept_id = rs.getInt("dept_id");
    			   list.add(new Emp(id, ename, job_id, mgr, joindate, salary, bonus, dept_id));
    		   }
    		} catch (SQLException e) {
    			e.printStackTrace();
    		} finally {
    			 // 8. 释放资源
    			JDBCUtils.close(rs, stmt, conn);
    		}
    		return list;
    	}
    }
  

测试结果：

[Emp [id=1001, name=孙悟空, job_id=4, mgr=1004, joindate=2000-12-17, salary=8000.0, bonus=0.0, dept_id=20], Emp [id=1002, name=卢俊义, job_id=3, mgr=1006, joindate=2001-02-20, salary=16000.0, bonus=3000.0, dept_id=30], Emp [id=1003, name=林冲, job_id=3, mgr=1006, joindate=2001-02-22, salary=12500.0, bonus=5000.0, dept_id=30], Emp [id=1004, name=唐僧, job_id=2, mgr=1009, joindate=2001-04-02, salary=29750.0, bonus=0.0, dept_id=20], Emp [id=1005, name=李逵, job_id=4, mgr=1006, joindate=2001-09-28, salary=12500.0, bonus=14000.0, dept_id=30], Emp [id=1006, name=宋江, job_id=2, mgr=1009, joindate=2001-05-01, salary=28500.0, bonus=0.0, dept_id=30], Emp [id=1007, name=刘备, job_id=2, mgr=1009, joindate=2001-09-01, salary=24500.0, bonus=0.0, dept_id=10], Emp [id=1008, name=猪八戒, job_id=4, mgr=1004, joindate=2007-04-19, salary=30000.0, bonus=0.0, dept_id=20], Emp [id=1009, name=罗贯中, job_id=1, mgr=0, joindate=2001-11-17, salary=50000.0, bonus=0.0, dept_id=10], Emp [id=1010, name=吴用, job_id=3, mgr=1006, joindate=2001-09-08, salary=15000.0, bonus=0.0, dept_id=30], Emp [id=1011, name=沙僧, job_id=4, mgr=1004, joindate=2007-05-23, salary=11000.0, bonus=0.0, dept_id=20], Emp [id=1012, name=李逵, job_id=4, mgr=1006, joindate=2001-12-03, salary=9500.0, bonus=0.0, dept_id=30], Emp [id=1013, name=小白龙, job_id=4, mgr=1004, joindate=2001-12-03, salary=30000.0, bonus=0.0, dept_id=20], Emp [id=1014, name=关羽, job_id=4, mgr=1007, joindate=2002-01-23, salary=13000.0, bonus=0.0, dept_id=10]]

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