SpringMVC 数据绑定
查看spring源码可以看出spring支持转换的数据类型：
org.springframework.beans.PropertyEditorRegistrySupport:
/** * Actually register the default editors for this registry instance. */ private void createDefaultEditors() { this.defaultEditors = new HashMap<Class, PropertyEditor>(64); // Simple editors, without parameterization capabilities. // The JDK does not contain a default editor for any of these target types. this.defaultEditors.put(Charset.class, new CharsetEditor()); this.defaultEditors.put(Class.class, new ClassEditor()); this.defaultEditors.put(Class[].class, new ClassArrayEditor()); this.defaultEditors.put(Currency.class, new CurrencyEditor()); this.defaultEditors.put(File.class, new FileEditor()); this.defaultEditors.put(InputStream.class, new InputStreamEditor()); this.defaultEditors.put(InputSource.class, new InputSourceEditor()); this.defaultEditors.put(Locale.class, new LocaleEditor()); this.defaultEditors.put(Pattern.class, new PatternEditor()); this.defaultEditors.put(Properties.class, new PropertiesEditor()); this.defaultEditors.put(Resource[].class, new ResourceArrayPropertyEditor()); this.defaultEditors.put(TimeZone.class, new TimeZoneEditor()); this.defaultEditors.put(URI.class, new URIEditor()); this.defaultEditors.put(URL.class, new URLEditor()); this.defaultEditors.put(UUID.class, new UUIDEditor()); // Default instances of collection editors. // Can be overridden by registering custom instances of those as custom editors. this.defaultEditors.put(Collection.class, new CustomCollectionEditor(Collection.class)); this.defaultEditors.put(Set.class, new CustomCollectionEditor(Set.class)); this.defaultEditors.put(SortedSet.class, new CustomCollectionEditor(SortedSet.class)); this.defaultEditors.put(List.class, new CustomCollectionEditor(List.class)); this.defaultEditors.put(SortedMap.class, new CustomMapEditor(SortedMap.class)); // Default editors for primitive arrays. this.defaultEditors.put(byte[].class, new ByteArrayPropertyEditor()); this.defaultEditors.put(char[].class, new CharArrayPropertyEditor()); // The JDK does not contain a default editor for char! this.defaultEditors.put(char.class, new CharacterEditor(false)); this.defaultEditors.put(Character.class, new CharacterEditor(true)); // Spring's CustomBooleanEditor accepts more flag values than the JDK's default editor. this.defaultEditors.put(boolean.class, new CustomBooleanEditor(false)); this.defaultEditors.put(Boolean.class, new CustomBooleanEditor(true)); // The JDK does not contain default editors for number wrapper types! // Override JDK primitive number editors with our own CustomNumberEditor. this.defaultEditors.put(byte.class, new CustomNumberEditor(Byte.class, false)); this.defaultEditors.put(Byte.class, new CustomNumberEditor(Byte.class, true)); this.defaultEditors.put(short.class, new CustomNumberEditor(Short.class, false)); this.defaultEditors.put(Short.class, new CustomNumberEditor(Short.class, true)); this.defaultEditors.put(int.class, new CustomNumberEditor(Integer.class, false)); this.defaultEditors.put(Integer.class, new CustomNumberEditor(Integer.class, true)); this.defaultEditors.put(long.class, new CustomNumberEditor(Long.class, false)); this.defaultEditors.put(Long.class, new CustomNumberEditor(Long.class, true)); this.defaultEditors.put(float.class, new CustomNumberEditor(Float.class, false)); this.defaultEditors.put(Float.class, new CustomNumberEditor(Float.class, true)); this.defaultEditors.put(double.class, new CustomNumberEditor(Double.class, false)); this.defaultEditors.put(Double.class, new CustomNumberEditor(Double.class, true)); this.defaultEditors.put(BigDecimal.class, new CustomNumberEditor(BigDecimal.class, true)); this.defaultEditors.put(BigInteger.class, new CustomNumberEditor(BigInteger.class, true)); // Only register config value editors if explicitly requested. if (this.configValueEditorsActive) { StringArrayPropertyEditor sae = new StringArrayPropertyEditor(); this.defaultEditors.put(String[].class, sae); this.defaultEditors.put(short[].class, sae); this.defaultEditors.put(int[].class, sae); this.defaultEditors.put(long[].class, sae); } }
下面挑选一些常用的数据类型，举例说明它们的绑定方式
1. 基本数据类型(以int为例，其他类似)：
Controller代码：
@RequestMapping("test.do") public void test(int num) { }
JSP表单代码：
<form action="test.do" method="post"> <input value="10" type="text"/> ...... </form>
表单中input的name值和Controller的参数变量名保持一致，就能完成基本数据类型的数据绑定，如果不一致可以使用@RequestParam标注实现。值得一提的是，如果Controller方法参数中定义的是基本数据类型，但是从jsp提交过来的数据为null或者""的话，会出现数据转换的异常。也就是说，必须保证表单传递过来的数据不能为null或""，所以，在开发过程中，对可能为空的数据，最好将参数数据类型定义成包装类型，具体参见下面的第二条。
2. 包装类型(以Integer为例，其他类似)：
Controller代码：
@RequestMapping("test.do") public void test(Integer num) { }
JSP表单代码：
<form action="test.do" method="post"> <input value="10" type="text"/> ...... </form>