JDBC之SqlHelper

SqlHelper工具类如下：

 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.ResultSetMetaData;
 import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;

 import org.cc.foo_006.DbUtil;

 /**
  * SQL执行工具类
  * @author CC11001100
  *
  */
 public class SqlHelper{

     /**
      * 执行sql dql语句
      * @param clazz
      * @param sql
      * @param args
      * @return
      */
     public <T> List<T> dql(Class<T> clazz,String sql,Object ...args){

         List<T> list=new ArrayList<>();

         Connection conn=null;
         PreparedStatement pstmt=null;
         ResultSet rs=null;

         try {
             conn=DbUtil.getInstance().getConnection();
             pstmt=conn.prepareStatement(sql);
             for(int i=0;i<args.length;i++){
                 pstmt.setObject(i+1,args[i]);
             }
             rs=pstmt.executeQuery();
             while(rs.next()){
                 Map<String,Object> map=new HashMap<>();
                 ResultSetMetaData meta=rs.getMetaData();
                 for(int i=1;i<=meta.getColumnCount();i++){
                     map.put(meta.getColumnLabel(i),rs.getObject(i));
                 }
                 T o=clazz.newInstance();
                 for(String key:map.keySet()){
                     ReflectionUtil.setFieldValue(o,key,map.get(key));
                 }
                 list.add(o);
             }
         } catch (SQLException e) {
             e.printStackTrace();
         } catch (NoSuchFieldException e) {
             e.printStackTrace();
         } catch (InstantiationException e) {
             e.printStackTrace();
         } catch (IllegalAccessException e) {
             e.printStackTrace();
         }finally{
             DbUtil.getInstance().close(conn,pstmt,rs);
         }
         return list;
     }

     /**
      * 执行sql dml语句
      * @param conn
      * @param sql
      * @param args
      * @throws SQLException
      */
     public void dml(Connection conn,String sql,Object ...args) throws SQLException{
         PreparedStatement pstmt=null;

         try {
             pstmt=conn.prepareStatement(sql);
             for(int i=0;i<args.length;i++){
                 pstmt.setObject(i+1,args[i]);
             }
             pstmt.executeUpdate();
         } catch (SQLException e) {
             e.printStackTrace();
             throw e;
         }finally{
             DbUtil.getInstance().close(pstmt);
         }
     }

 }

反射工具类如下：

 import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.util.Arrays;

 /**
  * 反射工具类
  * @author CC11001100
  *
  */
 public class ReflectionUtil {

     /**
      * 设置属性可访问
      * @param field
      */
     public static void makeFieldAccessible(Field field) {
         if (!Modifier.isPublic(field.getModifiers())) {
             field.setAccessible(true);
         }
     }

     /**
      * 设置方法可访问
      * @param method
      */
     public static void makeMethodAccessible(Method method) {
         if (!Modifier.isPublic(method.getModifiers())) {
             method.setAccessible(true);
         }
     }

     /**
      * 获取本类显示声明的属性
      * @param object
      * @param fieldName
      * @return
      */
     public static Field getDeclaredField(Object object, String fieldName) {
         try {
             return object.getClass().getDeclaredField(fieldName);
         } catch (NoSuchFieldException | SecurityException e) {
             e.printStackTrace();
         }
         return null;
     }

     /**
      * 获取属性值（自己的或继承来的）
      * @param object
      * @param fieldName
      * @return
      */
     public static Object getFieldValue(Object object, String fieldName) {
         try {
             Field field=getField(object,fieldName);
             if(field==null) return null;

             Field.setAccessible(new Field[]{field},true);
             return field.get(object);
         } catch (SecurityException | IllegalArgumentException | IllegalAccessException e) {
             e.printStackTrace();
         }
         return null;
     }

     /**
      * 设置属性的值（自己的或继承来的）
      * @param object
      * @param fieldName
      * @param fieldValue
      * @throws NoSuchFieldException
      */
     public static void setFieldValue(Object object, String fieldName, Object fieldValue) throws NoSuchFieldException {
         Field field=getField(object,fieldName);
         if(field==null) throw new NoSuchFieldException() ;

         try {
             Field.setAccessible(new Field[]{field},true);
             field.set(object,fieldValue);
         } catch (SecurityException | IllegalArgumentException | IllegalAccessException e) {
             e.printStackTrace();
         }
     }

     /**
      * 提取冗余代码：根据名字获取属性，然后setField or getField
      * @param object
      * @param fieldName
      * @return
      */
     private static Field getField(Object object,String fieldName){
         try {
             //从自己开始往上顺藤摸瓜
             Class<?> clazz=object.getClass();
             while(clazz!=Object.class){
                 Field[] fields=clazz.getDeclaredFields();
                 for(int i=0;i<fields.length;i++){
                     //子类不应该继承父类的private，所以无视父类们的private field
                     if(Modifier.isPrivate(fields[i].getModifiers()) && clazz!=object.getClass()) continue;
                     if(fieldName.equals(fields[i].getName())){
                         return fields[i];
                     }
                 }
                 clazz=clazz.getSuperclass();
             }
         } catch (IllegalArgumentException | SecurityException e) {
             e.printStackTrace();
         }
         return null;
     }

     /**
      * 获取在本类显示声明的方法
      * @param object
      * @param methodName
      * @param parameterTypes
      * @return
      */
     public static Method getDeclaredMethod(Object object, String methodName, Class<?>[] parameterTypes) {
         try {
             return object.getClass().getDeclaredMethod(methodName,parameterTypes);
         } catch (NoSuchMethodException | SecurityException e) {
             e.printStackTrace();
         }
         return null;
     }

     /**
      * 获得方法，无论是本类声明还是继承来的
      * @param object
      * @param methodName
      * @param parameterTypes
      * @return
      */
     private static Method getMethod(Object object, String methodName, Class<?>[] parameterTypes) {
         Class clazz=object.getClass();
         while(clazz!=Object.class){
             Method methods[]=clazz.getDeclaredMethods();
             Method.setAccessible(methods,true); //太挫了..
             for(int i=0;i<methods.length;i++){
                 //子类不应该操作父类的private method
                 if(Modifier.isPrivate(methods[i].getModifiers()) && clazz!=object.getClass()) continue;
                 //因为Class只有一份，所以可以借助内置的进行比较，如果**名称**和**参数（数量、位置、类型）**都相同，则认定为同一个方法，返回值修饰符等不予考虑
                 //这么做不能区分包装类型和基本类型，难道它们底层实现不一致？妈的我怎么知道... int.class!=Integer.class
                 if(methodName.equals(methods[i].getName()) && Arrays.equals(methods[i].getParameterTypes(),parameterTypes)) return methods[i];
             }
             clazz=clazz.getSuperclass();
         }
         return null;
     }

     /**
      * 调用方法（本类声明或继承而来）
      * @param object
      * @param methodName
      * @param parameterTypes
      * @param parameters
      * @return
      * @throws NoSuchMethodException
      */
     public static Object invokeMethod(Object object, String methodName, Class<?>[] parameterTypes,Object[] parameters) throws NoSuchMethodException {
         Method method=getMethod(object,methodName,parameterTypes);
         if(method==null) throw new NoSuchMethodException();

         try {
             return method.invoke(object,parameters);
         } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
             e.printStackTrace();
         }
         return null;
     }

 }

数据对象如下：

 public class User {

     private String id;
     private String username;
     private String passwd;
     private int power;

     @Override
     public String toString() {
         return "User [id=" + id + ", username=" + username + ", passwd=" + passwd + ", power=" + power + "]";
     }

     public int getPower() {
         return power;
     }

     public void setPower(int power) {
         this.power = power;
     }

     public String getId() {
         return id;
     }

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

     public String getUsername() {
         return username;
     }

     public void setUsername(String username) {
         this.username = username;
     }

     public String getPasswd() {
         return passwd;
     }

     public void setPasswd(String passwd) {
         this.passwd = passwd;
     }
 }

测试如下：

 import java.sql.Connection;
 import java.sql.SQLException;
 import java.util.List;

 import org.cc.foo_006.DbUtil;
 import org.junit.Test;

 public class Main_016 {

     @Test
     public void test_001(){

         Connection conn=null;

         try {
             conn=DbUtil.getInstance().getConnection();
             conn.setAutoCommit(false);

             SqlHelper sqlHelper=new SqlHelper();

             sqlHelper.dml(conn,"INSERT INTO t_user (id,username,passwd) VALUES (?,?,?)","1001","root","toor");
             sqlHelper.dml(conn,"INSERT INTO t_power (u_id,power) VALUES (?,?)","1001",7);

             conn.commit();
         } catch (SQLException e) {
             e.printStackTrace();
             try {
                 conn.rollback();
             } catch (SQLException e1) {
                 e1.printStackTrace();
             }
         }finally{
             DbUtil.getInstance().close(conn);
         }
     }

     @Test
     public void test_002(){

         SqlHelper sqlHelper=new SqlHelper();
         List<User> list=sqlHelper.dql(User.class,"SELECT t1.id,username,passwd,power FROM t_user AS t1 JOIN t_power AS t2 ON t1.id=t2.u_id WHERE t1.id=?","1001");

         for(User u:list){
             System.out.println(u);
         }

     }

 }

数据库语句如下：

 drop table if exists t_power;
 drop table if exists t_user;

 drop table if exists t_user;
 create table t_user(
     id varchar(20) primary key ,
     username varchar(20) not null,
     passwd varchar(20) not null
 )charset utf8;

 drop table if exists t_power;
 create table t_power (
     id int primary key auto_increment ,
     u_id varchar(20) ,
     power int ,
     constraint t_user_fk foreign key (u_id) references t_user(id)
 )charset utf8;