浅谈SpringMVC数据绑定-spring+springmvc+mybatis

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>

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，***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>

和基本数据类型基本一样，不同之处在于，JSP表单传递过来的数据可以为null或""，以上面代码为例，如果jsp中num为""或者表单中无num这个input，那么，Controller方法参数中的num值则为null。

3. 自定义对象类型：
Model代码：

public class User {

private String firstName;

private String lastName;

public String getFirstName() {

return firstName;

}

public void setFirstName(String firstName) {

this.firstName = firstName;

}

public String getLastName() {

return lastName;

}

public void setLastName(String lastName) {

this.lastName = lastName;

}

Controller代码：

@RequestMapping("test.do")

public void test(User user) {

}

JSP表单代码：

......

</form>

非常简单，只需将对象的属性名和input的name值一一对应即可。

4. 自定义复合对象类型：
Model代码：

public class ContactInfo {

private String tel;

private String address;

public String getTel() {

return tel;

}

public void setTel(String tel) {

this.tel = tel;

}

public String getAddress() {

return address;

}

public void setAddress(String address) {

this.address = address;

}

public class User {

private String firstName;

private String lastName;

private ContactInfo contactInfo;

public String getFirstName() {

return firstName;

}

public void setFirstName(String firstName) {

this.firstName = firstName;

}

public String getLastName() {

return lastName;

}

public void setLastName(String lastName) {

this.lastName = lastName;

}

public ContactInfo getContactInfo() {

return contactInfo;

}

public void setContactInfo(ContactInfo contactInfo) {

this.contactInfo = contactInfo;

}

Controller代码：

@RequestMapping("test.do")

public void test(User user) {

System.out.println(user.getFirstName());

System.out.println(user.getLastName());

System.out.println(user.getContactInfo().getTel());

System.out.println(user.getContactInfo().getAddress());

}

JSP表单代码：

</form>

User对象中有ContactInfo属性，Controller中的代码和第3点说的一致，但是，在jsp代码中，需要使用“属性名(对象类型的属性).属性名”来命名input的name。

5. List绑定：
List需要绑定在对象上，而不能直接写在Controller方法的参数中。
Model代码：

public class User {

private String firstName;

private String lastName;

public String getFirstName() {

return firstName;

}

public void setFirstName(String firstName) {

this.firstName = firstName;

}

public String getLastName() {

return lastName;

}

public void setLastName(String lastName) {

this.lastName = lastName;

}

public class UserListForm {

private List<User> users;

public List<User> getUsers() {

return users;

}

public void setUsers(List<User> users) {

this.users = users;

}

Controller代码：

@RequestMapping("test.do")

public void test(UserListForm userForm) {

for (User user : userForm.getUsers()) {

System.out.println(user.getFirstName() + " - " + user.getLastName());

}

JSP表单代码：

<table>

<thead>

<tr>

<th>First Name</th>

</tr>

</thead>

<tfoot>

<tr>

</tr>

</tfoot>

<tbody>

<tr>

</tr>

<tr>

</tr>

<tr>

</tr>

</tbody>

</table>

</form>

其实，这和第4点User对象中的contantInfo数据的绑定有点类似，但是这里的UserListForm对象里面的属性被定义成List，而不是普通自定义对象。所以，在JSP中需要指定List的下标。值得一提的是，Spring会创建一个以***下标值为size的List对象，所以，如果JSP表单中有动态添加行、删除行的情况，就需要特别注意，譬如一个表格，用户在使用过程中经过多次删除行、增加行的操作之后，下标值就会与实际大小不一致，这时候，List中的对象，只有在jsp表单中对应有下标的那些才会有值，否则会为null，看个例子：
JSP表单代码：

<table>

<thead>

<tr>

<th>First Name</th>

</tr>

</thead>

<tfoot>

<tr>

</tr>

</tfoot>

<tbody>

<tr>

</tr>

<tr>

</tr>

<tr>

</tr>

</tbody>

</table>

</form>

这个时候，Controller中的userForm.getUsers()获取到List的size为21，而且这21个User对象都不会为null，但是，第2到第19的User对象中的firstName和lastName都为null。打印结果：

aaa - bbb

ccc - ddd

null - null

eee - fff

6. Set绑定：
Set和List类似，也需要绑定在对象上，而不能直接写在Controller方法的参数中。但是，绑定Set数据时，必须先在Set对象中add相应的数量的模型对象。
Model代码：

public class User {

private String firstName;

private String lastName;

public String getFirstName() {

return firstName;

}

public void setFirstName(String firstName) {

this.firstName = firstName;

}

public String getLastName() {

return lastName;

}

public void setLastName(String lastName) {

this.lastName = lastName;

}

public class UserSetForm {

private Set<User> users = new HashSet<User>();

public UserSetForm(){

users.add(new User());

}

public Set<User> getUsers() {

return users;

}

public void setUsers(Set<User> users) {

this.users = users;

}

Controller代码：

@RequestMapping("test.do")

public void test(UserSetForm userForm) {

for (User user : userForm.getUsers()) {

System.out.println(user.getFirstName() + " - " + user.getLastName());

}

JSP表单代码：

<table>

<thead>

<tr>

<th>First Name</th>

</tr>

</thead>

<tfoot>

<tr>

</tr>

</tfoot>

<tbody>

<tr>

</tr>

<tr>

</tr>

<tr>

</tr>

</tbody>

</table>

</form>

基本和List绑定类似。
需要特别提醒的是，如果***下标值大于Set的size，则会抛出org.springframework.beans.InvalidPropertyException异常。所以，在使用时有些不便。暂时没找到解决方法，如果有网友知道，请回帖共享你的做法。

5. Map绑定：
Map最为灵活，它也需要绑定在对象上，而不能直接写在Controller方法的参数中。
Model代码：

public class User {

private String firstName;

private String lastName;

public String getFirstName() {

return firstName;

}

public void setFirstName(String firstName) {

this.firstName = firstName;

}

public String getLastName() {

return lastName;

}

public void setLastName(String lastName) {

this.lastName = lastName;

}

public class UserMapForm {

private Map<String, User> users;

public Map<String, User> getUsers() {

return users;

}

public void setUsers(Map<String, User> users) {

this.users = users;

}

Controller代码：

@RequestMapping("test.do")

public void test(UserMapForm userForm) {

for (Map.Entry<String, User> entry : userForm.getUsers().entrySet()) {

System.out.println(entry.getKey() + ": " + entry.getValue().getFirstName() + " - " +

entry.getValue().getLastName());

}

JSP表单代码：

<table>

<thead>

<tr>

<th>First Name</th>

</tr>

</thead>

<tfoot>

<tr>

</tr>

</tfoot>

<tbody>

<tr>

</tr>

<tr>

</tr>

<tr>

</tr>

</tbody>

</table>

</form>

打印结果：

x: aaa - bbb

y: ccc - ddd

z: eee - fff

【编辑推荐】

责任编辑：赵宁宁

SpringMVC