(0!=0)==true? 记一个匪夷所思的问题

最近换了份工作，公司的开发框架是基于SSH自己搭建的。这个问题是我在解决一个需求的时候遇到的，其实解决这个疑惑的过程也就是读框架源码的过程，特此记录一下。

问题：ba.getState()!=CbBankAccount.STATE_NORMAL

在二者的类型都是Integer的且字面值均为0的情况下返回了true。

我们知道Java中整型的-128~127存在JVM的运行时常量池中，当比较处于这个范围的的整型值时比较的是字面值，反之比较的是引用堆中的对象的地址。

而在我遇到的情况下二者都是0。想到可能是在某处代码调用ba.setState(Integer i)赋值时做了手脚。

接下来就是跟代码的过程了。以下代码有部分删改。

ba先从数据库查出来，再从前台请求中获取对应字段赋值。

 ba = (CbBankAccount) super.getBeanForUpdate(CbBankAccount.class, ba);

public <T> T getBeanForUpdate(Class<T> clazz, Object obj) {
        Assert.notNull(obj);
        Assert.notNull(clazz);
        return HttpUtils.getBean(getRequest(), clazz, obj);
    }

public static <T> T getBean(HttpServletRequest request, Class<T> c,
            Object obj) {
        Map<String, Object> paramMap = request.getParameterMap();
        Object value = null;
        Class[] paramTypes = new Class[1];

        try {
            Field[] f = c.getDeclaredFields();
            List<Field[]> flist = new ArrayList<Field[]>();
            flist.add(f);
            Class superClazz = c.getSuperclass(); // 获取父类,如果父类存在则取父类的Field
            while (superClazz != null) {
                f = superClazz.getDeclaredFields();
                flist.add(f);
                superClazz = superClazz.getSuperclass();
            }
            for (Field[] temp : flist) {
                for (Field field : temp) {
                    String fName = field.getName();

                    value = paramMap.get(fName);
                    if (value != null) {
                        paramTypes[0] = field.getType();
                        Method method = null;
                        StringBuffer methodName = new StringBuffer("set");
                        methodName.append(fName.substring(0, 1).toUpperCase());
                        methodName.append(fName.substring(1, fName.length()));
                        method = c.getMethod(methodName.toString(), paramTypes);
                        method.invoke(obj, getValue(request, fName,
                                paramTypes[0]));//从请求中获得字段对应值并赋值
                    }

                }
            }
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (SecurityException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

        return (T) obj;
    }

....

最终在转换数字的地方找到了答案（使用的是org.apache.commons.beanutils.converters.NumberConverter）

private Number toNumber(Class sourceType, Class targetType, Number value) {

        // Correct Number type already
        if (targetType.equals(value.getClass())) {
            return value;
        }

        // Byte
        if (targetType.equals(Byte.class)) {
            long longValue = value.longValue();
            if (longValue > Byte.MAX_VALUE) {
                throw new ConversionException(toString(sourceType) + " value '" + value
                        + "' is too large for " + toString(targetType));
            }
            if (longValue < Byte.MIN_VALUE) {
                throw new ConversionException(toString(sourceType) + " value '" + value
                        + "' is too small " + toString(targetType));
            }
            return new Byte(value.byteValue());
        }

        // Short
        if (targetType.equals(Short.class)) {
            long longValue = value.longValue();
            if (longValue > Short.MAX_VALUE) {
                throw new ConversionException(toString(sourceType) + " value '" + value
                        + "' is too large for " + toString(targetType));
            }
            if (longValue < Short.MIN_VALUE) {
                throw new ConversionException(toString(sourceType) + " value '" + value
                        + "' is too small " + toString(targetType));
            }
            return new Short(value.shortValue());
        }

        // Integer
        if (targetType.equals(Integer.class)) {
            long longValue = value.longValue();
            if (longValue > Integer.MAX_VALUE) {
                throw new ConversionException(toString(sourceType) + " value '" + value
                        + "' is too large for " + toString(targetType));
            }
            if (longValue < Integer.MIN_VALUE) {
                throw new ConversionException(toString(sourceType) + " value '" + value
                        + "' is too small " + toString(targetType));
            }
            return new Integer(value.intValue());
        }

        // Long
        if (targetType.equals(Long.class)) {
            return new Long(value.longValue());
        }

        // Float
        if (targetType.equals(Float.class)) {
            if (value.doubleValue() > Float.MAX_VALUE) {
                throw new ConversionException(toString(sourceType) + " value '" + value
                        + "' is too large for " + toString(targetType));
            }
            return new Float(value.floatValue());
        }

        // Double
        if (targetType.equals(Double.class)) {
            return new Double(value.doubleValue());
        }

        // BigDecimal
        if (targetType.equals(BigDecimal.class)) {
            if (value instanceof Float || value instanceof Double) {
                return new BigDecimal(value.toString());
            } else if (value instanceof BigInteger) {
                return new BigDecimal((BigInteger)value);
            } else {
                return BigDecimal.valueOf(value.longValue());
            }
        }

        // BigInteger
        if (targetType.equals(BigInteger.class)) {
            if (value instanceof BigDecimal) {
                return ((BigDecimal)value).toBigInteger();
            } else {
                return BigInteger.valueOf(value.longValue());
            }
        }

        String msg = toString(getClass()) + " cannot handle conversion to '"
                   + toString(targetType) + "'";
        if (log().isWarnEnabled()) {
            log().warn("    " + msg);
        }
        throw new ConversionException(msg);

    }

return new Integer(value.intValue());创建了一个新的对象。故出现了上边的问题。

遇到问题还是要跟源码分析才能得到结果啊！