利用反射和JDBC元数据实现更加通用的查询方法

 package com.at221.jdbc;

 import java.io.IOException;
 import java.io.InputStream;
 import java.sql.*;
 import java.util.Properties;

 import com.mysql.jdbc.Connection;

 public class JDBCTools {
     public static void release(Statement sta,java.sql.Connection con,ResultSet rs){
         if(sta != null){
             try{
                 sta.close();
             }catch(Exception e){
                 e.getStackTrace();
             }
         }

         if(con != null){
             try{
                 con.close();
             }catch(Exception e){
                 e.getStackTrace();
             }
         }

         if(rs != null){
             try {
                 rs.close();
             } catch (SQLException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }
         }

     }

     public static void release(Statement sta,java.sql.Connection con){
         if(sta != null){
             try{
                 sta.close();
             }catch(Exception e){
                 e.getStackTrace();
             }
         }

         if(con != null){
             try{
                 con.close();
             }catch(Exception e){
                 e.getStackTrace();
             }
         }

     }

     public static Connection getConnec() throws SQLException, IOException, ClassNotFoundException,
     InstantiationException, IllegalAccessException{
         String driverClass = null;
         String jdbcUrl = null;
         String user = null;
         String password = null;

         //利用配置文件，来更改数据库的配置
         InputStream is = JDBCTools.class.getClassLoader().getResourceAsStream("jdbc.properties");
         Properties p = new Properties();
         p.load(is);
         driverClass = p.getProperty("driver");
 //        System.out.println(driverClass);

         jdbcUrl = p.getProperty("jdbcUrl");
 //        System.out.println(jdbcUrl);

         user = p.getProperty("user");
 //        System.out.println(driverClass);

         password = p.getProperty("password");
 //        System.out.println(password);

         Properties info = new Properties();
         info.put("user", user);
         info.put("password", password);
         DriverManager.registerDriver((Driver)Class.forName(driverClass).newInstance());

         Connection connec = (Connection)DriverManager.getConnection(jdbcUrl, user, password);
 //        System.out.println(connec);
         return connec;
     }
 }

 package com.at221.jdbc;

 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.util.HashMap;
 import java.util.Map;

 import org.junit.Test;

 import com.mysql.jdbc.ResultSetMetaData;

 public class TestReflection {
     @Test
     public void test(){
         String sql = "SELECT id Id,name Name,birth Birth,email Email from student where id = ?";
         Student s = (Student)getStudent(Student.class,sql,3);
         System.out.println(s);
     }
     public <T> Object getStudent(Class<T> clazz,String sql,Object ... args ){
         Connection conn = null;
         PreparedStatement ps = null;
         ResultSet rs = null;
         ResultSetMetaData rsmd = null;
         T entity = null;
         try {
             //1.SQL语句进行配置
             conn = JDBCTools.getConnec();
             ps = conn.prepareStatement(sql);
             //①给SQL语句中的通配符赋值

             for(int i = 0; i < args.length; i++){
                 ps.setObject(i+1, args[i]);
             }
             //②利用SQL进行查询得到结果集
             rs = ps.executeQuery();
             //2.创建类的对象
             entity = clazz.newInstance();
             //3.利用jdbc元数据来获得列的别名,为map中的键值对进行赋值
             rsmd = (ResultSetMetaData)rs.getMetaData();

             Map<String, Object> value = new HashMap<String, Object>();
             if(rs.next()){
                 for(int i = 0; i < rsmd.getColumnCount(); i++){
                     String key = rsmd.getColumnLabel(i+1);
                     Object obj = rs.getObject(i+1);
                     value.put(key, obj);
                 }
             }
             //4.利用得到的map进行对创建的对象进行赋值
             if(value.size() > 0){
                 for(Map.Entry<String, Object> entry : value.entrySet()){
                     String column = entry.getKey();
                     Object columnValue = entry.getValue();
                     RecflectionUtils.setFieldValue(entity, column, columnValue);
                 }
             }

         } catch(Exception e){
             e.printStackTrace();
         }finally {
             JDBCTools.release(ps, conn);

         }
         return entity;
     }
 }

 package com.at221.jdbc;

 import java.sql.Date;

 public class Student {
     private int id;
     private String name = null;
     private Date birth = null;
     private String email = null;

     public Student(int id, String name, Date birth, String email) {
         super();
         this.id = id;
         this.name = name;
         this.birth = birth;
         this.email = email;
     }

     public Student() {
         super();
     }

     public int getId() {
         return id;
     }

     public void setId(Integer id) {
         this.id = id.intValue();
     }

     public String getName() {
         return name;
     }

     public void setName(String name) {
         this.name = name;
     }

     public Date getBirth() {
         return birth;
     }

     public void setBirth(Date birth) {
         this.birth = birth;
     }

     public String getEmail() {
         return email;
     }

     public void setEmail(String email) {
         this.email = email;
     }

     @Override
     public String toString() {
         return "Student [id=" + id + ", name=" + name
                 + ", birth=" + birth + ", email=" + email + "]";
     }

 }