遇到了若干问题：
1.从oracle返回的列名都是大写，再用反射，就找不到相对应得 名字
2.oracle 中number类型 返回来，就变成了BigDecimal
public static void main(String[] args){String sql = "SELECT IDCARD , examcard , "+ "studentname ,"+ "lacation LoCATION,grade "+ " FROM student WHERE IDCARD = ?";Student s = get(Student.class, sql, 7);System.out.println(s);}//String sql = "SELECT id, name, email, birth "<span style="white-space:pre"></span>//<span style="white-space:pre"></span>+ "FROM customers WHERE id = ?";public static <T> T get(Class<T> clazz, String sql, Object… args) {T entity = null;Connection connection = null;PreparedStatement preparedStatement = null;ResultSet resultSet = null;try {//1. 得到 ResultSet 对象connection = JDBC_Tools.getConnection();preparedStatement = connection.prepareStatement(sql);for (int i = 0; i < args.length; i++) {preparedStatement.setObject(i + 1, args[i]);}resultSet = preparedStatement.executeQuery();//2. 得到 ResultSetMetaData 对象ResultSetMetaData rsmd = resultSet.getMetaData();//3. 创建一个 Map<String, Object> 对象, 键: SQL 查询的列的别名,//值: 列的值Map<String, Object> values = new HashMap<>();//4. 处理结果集. 利用 ResultSetMetaData 填充 3 对应的 Map 对象if(resultSet.next()){for(int i = 0; i < rsmd.getColumnCount(); i++){//从 ResultSetMetaData 获取列的别名String columnLabel = rsmd.getColumnLabel(i + 1);//从 结果集 中获取列的值Object columnValue = resultSet.getObject(i + 1);values.put(columnLabel, columnValue);}}//5. 若 Map 不为空集, 利用反射创建 clazz 对应的对象if(values.size() > 0){entity = clazz.newInstance();//5. 遍历 Map 对象, 利用反射为 Class 对象的对应的属性赋值.for(Map.Entry<String, Object> entry: values.entrySet()){String fieldName = entry.getKey();Object value = entry.getValue();//System.out.println(fieldName+":"+value);ReflectionUtils.setFieldValue(entity, fieldName, value); //出问题//System.out.println(ReflectionUtils.getDeclaredField(entity,fieldName));}}} catch (Exception e) {e.printStackTrace();} finally {JDBC_Tools.relaseSource(resultSet, connection, preparedStatement);}return entity;}}
ReflectionUtils.setFieldValue(entity, fieldName, value);出问题
java.lang.IllegalArgumentException: Can not set int field xuezaipiao3.Student.GRADE to java.math.BigDecimalat sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:164)at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:168)at sun.reflect.UnsafeIntegerFieldAccessorImpl.set(UnsafeIntegerFieldAccessorImpl.java:98)at java.lang.reflect.Field.set(Field.java:741)at xuezaipiao3.ReflectionUtils.setFieldValue(ReflectionUtils.java:156)at xuezaipiao3.ThinkInJDBC.get(ThinkInJDBC.java:77)at xuezaipiao3.ThinkInJDBC.main(ThinkInJDBC.java:45)Student [IDCARD=0, EXAMCARD=0, STUDENTNAME=null, LOCATION=7, GRADE=0]
Oracle 中 number类型 通过ResultSet 的 getObject() 返回的是BigDecimal ，无法强制转化，，而且 ResultSetMetaData 的 getColumnLabel() 取回的 列的别名是大写
MySQL不存在这样的问题
用的 Oracle 10g
ReflectionUtils
package xuezaipiao3;import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.lang.reflect.Modifier;import java.lang.reflect.ParameterizedType;import java.lang.reflect.Type;/** * 反射的 Utils 函数集合 * 提供访问私有变量, 获取泛型类型 Class, 提取集合中元素属性等 Utils 函数 * @author Administrator * */public class ReflectionUtils {/** * 通过反射, 获得定义 Class 时声明的父类的泛型参数的类型 * 如: public EmployeeDao extends BaseDao<Employee, String> * @param <T> * @param clazz * @param index * @return */@SuppressWarnings("unchecked")public static Class getSuperClassGenricType(Class clazz, int index){Type genType = clazz.getGenericSuperclass();if(!(genType instanceof ParameterizedType)){return Object.class;}Type [] params = ((ParameterizedType)genType).getActualTypeArguments();if(index >= params.length || index < 0){return Object.class;}if(!(params[index] instanceof Class)){return Object.class;}return (Class) params[index];}/** * 通过反射, 获得 Class 定义中声明的父类的泛型参数类型 * 如: public EmployeeDao extends BaseDao<Employee, String> * @param <T> * @param clazz * @return */@SuppressWarnings("unchecked")public static<T> Class<T> getSuperGenericType(Class<T> clazz){return getSuperClassGenricType(clazz, 0);}/** * 循环向上转型, 获取对象的 DeclaredMethod * @param object * @param methodName * @param parameterTypes * @return */public static Method getDeclaredMethod(Object object, String methodName, Class<?>[] parameterTypes){for(Class<?> superClass = object.getClass(); superClass != Object.class; superClass = superClass.getSuperclass()){try {//superClass.getMethod(methodName, parameterTypes);return superClass.getDeclaredMethod(methodName, parameterTypes);} catch (NoSuchMethodException e) {//Method 不在当前类定义, 继续向上转型}//..}return null;}/** * 使 filed 变为可访问 * @param field */public static void makeAccessible(Field field){if(!Modifier.isPublic(field.getModifiers())){field.setAccessible(true);}}/** * 循环向上转型, 获取对象的 DeclaredField * @param object * @param filedName * @return */public static Field getDeclaredField(Object object, String filedName){for(Class<?> superClass = object.getClass(); superClass != Object.class; superClass = superClass.getSuperclass()){try {return superClass.getDeclaredField(filedName);} catch (NoSuchFieldException e) {//Field 不在当前类定义, 继续向上转型}}return null;}/** * 直接调用对象方法, 而忽略修饰符(private, protected) * @param object * @param methodName * @param parameterTypes * @param parameters * @return * @throws InvocationTargetException * @throws IllegalArgumentException */public static Object invokeMethod(Object object, String methodName, Class<?> [] parameterTypes,Object [] parameters) throws InvocationTargetException{Method method = getDeclaredMethod(object, methodName, parameterTypes);if(method == null){throw new IllegalArgumentException("Could not find method [" + methodName + "] on target [" + object + "]");}method.setAccessible(true);try {return method.invoke(object, parameters);} catch(IllegalAccessException e) {System.out.println("不可能抛出的异常");}return null;}/** * 直接设置对象属性值, 忽略 private/protected 修饰符, 也不经过 setter * @param object * @param fieldName * @param value */public static void setFieldValue(Object object, String fieldName, Object value){Field field = getDeclaredField(object, fieldName);if (field == null)throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + object + "]");makeAccessible(field);try {field.set(object, value);} catch (IllegalAccessException e) {System.out.println("不可能抛出的异常");}}/** * 直接读取对象的属性值, 忽略 private/protected 修饰符, 也不经过 getter * @param object * @param fieldName * @return */public static Object getFieldValue(Object object, String fieldName){Field field = getDeclaredField(object, fieldName);if (field == null)throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + object + "]");makeAccessible(field);Object result = null;try {result = field.get(object);} catch (IllegalAccessException e) {System.out.println("不可能抛出的异常");}return result;}}
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