JDBC之SqlHelper
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SqlHelper工具类如下：
1 import java.sql.Connection; 2 import java.sql.PreparedStatement; 3 import java.sql.ResultSet; 4 import java.sql.ResultSetMetaData; 5 import java.sql.SQLException; 6 import java.util.ArrayList; 7 import java.util.HashMap; 8 import java.util.List; 9 import java.util.Map; 10 11 import org.cc.foo_006.DbUtil; 12 13 /** 14 * SQL执行工具类 15 * @author CC11001100 16 * 17 */ 18 public class SqlHelper{ 19 20 /** 21 * 执行sql dql语句 22 * @param clazz 23 * @param sql 24 * @param args 25 * @return 26 */ 27 public <T> List<T> dql(Class<T> clazz,String sql,Object ...args){ 28 29 List<T> list=new ArrayList<>(); 30 31 Connection conn=null; 32 PreparedStatement pstmt=null; 33 ResultSet rs=null; 34 35 try { 36 conn=DbUtil.getInstance().getConnection(); 37 pstmt=conn.prepareStatement(sql); 38 for(int i=0;i<args.length;i++){ 39 pstmt.setObject(i+1,args[i]); 40 } 41 rs=pstmt.executeQuery(); 42 while(rs.next()){ 43 Map<String,Object> map=new HashMap<>(); 44 ResultSetMetaData meta=rs.getMetaData(); 45 for(int i=1;i<=meta.getColumnCount();i++){ 46 map.put(meta.getColumnLabel(i),rs.getObject(i)); 47 } 48 T o=clazz.newInstance(); 49 for(String key:map.keySet()){ 50 ReflectionUtil.setFieldValue(o,key,map.get(key)); 51 } 52 list.add(o); 53 } 54 } catch (SQLException e) { 55 e.printStackTrace(); 56 } catch (NoSuchFieldException e) { 57 e.printStackTrace(); 58 } catch (InstantiationException e) { 59 e.printStackTrace(); 60 } catch (IllegalAccessException e) { 61 e.printStackTrace(); 62 }finally{ 63 DbUtil.getInstance().close(conn,pstmt,rs); 64 } 65 return list; 66 } 67 68 /** 69 * 执行sql dml语句 70 * @param conn 71 * @param sql 72 * @param args 73 * @throws SQLException 74 */ 75 public void dml(Connection conn,String sql,Object ...args) throws SQLException{ 76 PreparedStatement pstmt=null; 77 78 try { 79 pstmt=conn.prepareStatement(sql); 80 for(int i=0;i<args.length;i++){ 81 pstmt.setObject(i+1,args[i]); 82 } 83 pstmt.executeUpdate(); 84 } catch (SQLException e) { 85 e.printStackTrace(); 86 throw e; 87 }finally{ 88 DbUtil.getInstance().close(pstmt); 89 } 90 } 91 92 }
反射工具类如下：
1 import java.lang.reflect.Field; 2 import java.lang.reflect.InvocationTargetException; 3 import java.lang.reflect.Method; 4 import java.lang.reflect.Modifier; 5 import java.util.Arrays; 6 7 /** 8 * 反射工具类 9 * @author CC11001100 10 * 11 */ 12 public class ReflectionUtil { 13 14 /** 15 * 设置属性可访问 16 * @param field 17 */ 18 public static void makeFieldAccessible(Field field) { 19 if (!Modifier.isPublic(field.getModifiers())) { 20 field.setAccessible(true); 21 } 22 } 23 24 /** 25 * 设置方法可访问 26 * @param method 27 */ 28 public static void makeMethodAccessible(Method method) { 29 if (!Modifier.isPublic(method.getModifiers())) { 30 method.setAccessible(true); 31 } 32 } 33 34 /** 35 * 获取本类显示声明的属性 36 * @param object 37 * @param fieldName 38 * @return 39 */ 40 public static Field getDeclaredField(Object object, String fieldName) { 41 try { 42 return object.getClass().getDeclaredField(fieldName); 43 } catch (NoSuchFieldException | SecurityException e) { 44 e.printStackTrace(); 45 } 46 return null; 47 } 48 49 /** 50 * 获取属性值（自己的或继承来的） 51 * @param object 52 * @param fieldName 53 * @return 54 */ 55 public static Object getFieldValue(Object object, String fieldName) { 56 try { 57 Field field=getField(object,fieldName); 58 if(field==null) return null; 59 60 Field.setAccessible(new Field[]{field},true); 61 return field.get(object); 62 } catch (SecurityException | IllegalArgumentException | IllegalAccessException e) { 63 e.printStackTrace(); 64 } 65 return null; 66 } 67 68 /** 69 * 设置属性的值（自己的或继承来的） 70 * @param object 71 * @param fieldName 72 * @param fieldValue 73 * @throws NoSuchFieldException 74 */ 75 public static void setFieldValue(Object object, String fieldName, Object fieldValue) throws NoSuchFieldException { 76 Field field=getField(object,fieldName); 77 if(field==null) throw new NoSuchFieldException() ; 78 79 try { 80 Field.setAccessible(new Field[]{field},true); 81 field.set(object,fieldValue); 82 } catch (SecurityException | IllegalArgumentException | IllegalAccessException e) { 83 e.printStackTrace(); 84 } 85 } 86 87 /** 88 * 提取冗余代码：根据名字获取属性，然后setField or getField 89 * @param object 90 * @param fieldName 91 * @return 92 */ 93 private static Field getField(Object object,String fieldName){ 94 try { 95 //从自己开始往上顺藤摸瓜 96 Class<?> clazz=object.getClass(); 97 while(clazz!=Object.class){ 98 Field[] fields=clazz.getDeclaredFields(); 99 for(int i=0;i<fields.length;i++){ 100 //子类不应该继承父类的private，所以无视父类们的private field 101 if(Modifier.isPrivate(fields[i].getModifiers()) && clazz!=object.getClass()) continue; 102 if(fieldName.equals(fields[i].getName())){ 103 return fields[i]; 104 } 105 } 106 clazz=clazz.getSuperclass(); 107 } 108 } catch (IllegalArgumentException | SecurityException e) { 109 e.printStackTrace(); 110 } 111 return null; 112 } 113 114 /** 115 * 获取在本类显示声明的方法 116 * @param object 117 * @param methodName 118 * @param parameterTypes 119 * @return 120 */ 121 public static Method getDeclaredMethod(Object object, String methodName, Class<?>[] parameterTypes) { 122 try { 123 return object.getClass().getDeclaredMethod(methodName,parameterTypes); 124 } catch (NoSuchMethodException | SecurityException e) { 125 e.printStackTrace(); 126 } 127 return null; 128 } 129 130 /** 131 * 获得方法，无论是本类声明还是继承来的 132 * @param object 133 * @param methodName 134 * @param parameterTypes 135 * @return 136 */ 137 private static Method getMethod(Object object, String methodName, Class<?>[] parameterTypes) { 138 Class clazz=object.getClass(); 139 while(clazz!=Object.class){ 140 Method methods[]=clazz.getDeclaredMethods(); 141 Method.setAccessible(methods,true); //太挫了.. 142 for(int i=0;i<methods.length;i++){ 143 //子类不应该操作父类的private method 144 if(Modifier.isPrivate(methods[i].getModifiers()) && clazz!=object.getClass()) continue; 145 //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 146 //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 147 if(methodName.equals(methods[i].getName()) && Arrays.equals(methods[i].getParameterTypes(),parameterTypes)) return methods[i]; 148 } 149 clazz=clazz.getSuperclass(); 150 } 151 return null; 152 } 153 154 /** 155 * 调用方法（本类声明或继承而来） 156 * @param object 157 * @param methodName 158 * @param parameterTypes 159 * @param parameters 160 * @return 161 * @throws NoSuchMethodException 162 */ 163 public static Object invokeMethod(Object object, String methodName, Class<?>[] parameterTypes,Object[] parameters) throws NoSuchMethodException { 164 Method method=getMethod(object,methodName,parameterTypes); 165 if(method==null) throw new NoSuchMethodException(); 166 167 try { 168 return method.invoke(object,parameters); 169 } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) { 170 e.printStackTrace(); 171 } 172 return null; 173 } 174 175 }
数据对象如下：
1 public class User { 2 3 private String id; 4 private String username; 5 private String passwd; 6 private int power; 7 8 @Override 9 public String toString() { 10 return "User [id=" + id + ", username=" + username + ", passwd=" + passwd + ", power=" + power + "]"; 11 } 12 13 public int getPower() { 14 return power; 15 } 16 17 public void setPower(int power) { 18 this.power = power; 19 } 20 21 public String getId() { 22 return id; 23 } 24 25 public void setId(String id) { 26 this.id = id; 27 } 28 29 public String getUsername() { 30 return username; 31 } 32 33 public void setUsername(String username) { 34 this.username = username; 35 } 36 37 public String getPasswd() { 38 return passwd; 39 } 40 41 public void setPasswd(String passwd) { 42 this.passwd = passwd; 43 } 44 }
测试如下：
1 import java.sql.Connection; 2 import java.sql.SQLException; 3 import java.util.List; 4 5 import org.cc.foo_006.DbUtil; 6 import org.junit.Test; 7 8 public class Main_016 { 9 10 @Test 11 public void test_001(){ 12 13 Connection conn=null; 14 15 try { 16 conn=DbUtil.getInstance().getConnection(); 17 conn.setAutoCommit(false); 18 19 SqlHelper sqlHelper=new SqlHelper(); 20 21 sqlHelper.dml(conn,"INSERT INTO t_user (id,username,passwd) VALUES (?,?,?)","1001","root","toor"); 22 sqlHelper.dml(conn,"INSERT INTO t_power (u_id,power) VALUES (?,?)","1001",7); 23 24 conn.commit(); 25 } catch (SQLException e) { 26 e.printStackTrace(); 27 try { 28 conn.rollback(); 29 } catch (SQLException e1) { 30 e1.printStackTrace(); 31 } 32 }finally{ 33 DbUtil.getInstance().close(conn); 34 } 35 } 36 37 38 @Test 39 public void test_002(){ 40 41 SqlHelper sqlHelper=new SqlHelper(); 42 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"); 43 44 for(User u:list){ 45 System.out.println(u); 46 } 47 48 } 49 50 51 }
数据库语句如下：
1 drop table if exists t_power; 2 drop table if exists t_user; 3 4 drop table if exists t_user; 5 create table t_user( 6 id varchar(20) primary key , 7 username varchar(20) not null, 8 passwd varchar(20) not null 9 )charset utf8; 10 11 12 drop table if exists t_power; 13 create table t_power ( 14 id int primary key auto_increment , 15 u_id varchar(20) , 16 power int , 17 constraint t_user_fk foreign key (u_id) references t_user(id) 18 )charset utf8;
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