springMVC对简单对象、Set、List、Map的数据绑定和常见问题
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1、相关的类:查看spring源码可以看出spring支持转换的数据类型:
org.springframework.beans.PropertyEditorRegistrySupport:
-
- private void createDefaultEditors() {
- this.defaultEditors = new HashMap(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);
- }
- }
2、基本数据类型绑定:
- @RequestMapping("test.do")
- public void test(int num) {
-
- }
- "test.do" method="post">
- "num" value="10" type="text"/>
- ......
-
注意: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。
3、包装类型
- @RequestMapping("test.do")
- public void test(Integer num) {
-
- }
- "test.do" method="post">
- "num" value="10" type="text"/>
- ......
-
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。
4、自定义对象类型
- public class User {
-
- private String firstName;
-
- private String lastName;
-
- ...
-
- }
- @RequestMapping("test.do")
- public void test(User user) {
-
- }
- "test.do" method="post">
- "firstName" value="张" type="text"/>
- "lastName" value="三" type="text"/>
- ......
-
只需将对象的属性名和input的name值一一对应即可。
5、自定义复合对象类型
- public class ContactInfo {
-
- private String tel;
-
- private String address;
-
- 。。。
-
- }
-
- public class User {
-
- private String firstName;
-
- private String lastName;
-
- private ContactInfo contactInfo;
-
- 。。。
-
- }
- @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());
- }
- <</span>form action="test.do" method="post">
- <</span>input name="firstName" value="张" /><</span>br>
- <</span>input name="lastName" value="三" /><</span>br>
- <</span>input name="contactInfo.tel" value="13809908909" /><</span>br>
- <</span>input name="contactInfo.address" value="北京海淀" /><</span>br>
- <</span>input type="submit" value="Save" />
- </</span>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。
6、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。
- public class User {
-
- private String firstName;
-
- private String lastName;
-
- 。。。
-
- }
-
- public class UserListForm {
-
- private List users;
-
- 。。。
-
- }
- @RequestMapping("test.do")
- public void test(UserListForm userForm) {
- for (User user : userForm.getUsers()) {
- System.out.println(user.getFirstName() + " - " + user.getLastName());
- }
- }
- <</span>form action="test.do" method="post">
- <</span>table>
- <</span>thead>
- <</span>tr>
- <</span>th>First Name</</span>th>
- <</span>th>Last Name</</span>th>
- </</span>tr>
- </</span>thead>
- <</span>tfoot>
- <</span>tr>
- <</span>td colspan="2"><</span>input type="submit" value="Save" /></</span>td>
- </</span>tr>
- </</span>tfoot>
- <</span>tbody>
- <</span>tr>
- <</span>td><</span>input name="users[0].firstName" value="aaa" /></</span>td>
- <</span>td><</span>input name="users[0].lastName" value="bbb" /></</span>td>
- </</span>tr>
- <</span>tr>
- <</span>td><</span>input name="users[1].firstName" value="ccc" /></</span>td>
- <</span>td><</span>input name="users[1].lastName" value="ddd" /></</span>td>
- </</span>tr>
- <</span>tr>
- <</span>td><</span>input name="users[2].firstName" value="eee" /></</span>td>
- <</span>td><</span>input name="users[2].lastName" value="fff" /></</span>td>
- </</span>tr>
- </</span>tbody>
- </</span>table>
- </</span>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会创建一个以最大下标值为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:
- <</span>form action="test.do" method="post">
- <</span>table>
- <</span>thead>
- <</span>tr>
- <</span>th>First Name</</span>th>
- <</span>th>Last Name</</span>th>
- </</span>tr>
- </</span>thead>
- <</span>tfoot>
- <</span>tr>
- <</span>td colspan="2"><</span>input type="submit" value="Save" /></</span>td>
- </</span>tr>
- </</span>tfoot>
- <</span>tbody>
- <</span>tr>
- <</span>td><</span>input name="users[0].firstName" value="aaa" /></</span>td>
- <</span>td><</span>input name="users[0].lastName" value="bbb" /></</span>td>
- </</span>tr>
- <</span>tr>
- <</span>td><</span>input name="users[1].firstName" value="ccc" /></</span>td>
- <</span>td><</span>input name="users[1].lastName" value="ddd" /></</span>td>
- </</span>tr>
- <</span>tr>
- <</span>td><</span>input name="users[20].firstName" value="eee" /></</span>td>
- <</span>td><</span>input name="users[20].lastName" value="fff" /></</span>td>
- </</span>tr>
- </</span>tbody>
- </</span>table>
- </</span>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
- null - null
- null - null
- null - null
- null - null
- null - null
- null - null
- null - null
- null - null
- null - null
- null - null
- null - null
- null - null
- null - null
- null - null
- null - null
- null - null
- null - null
- eee - fff
7、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。
- public class User {
-
- private String firstName;
-
- private String lastName;
-
- 。。。
-
- }
-
- public class UserSetForm {
-
- private Set users = new HashSet();
-
- public UserSetForm(){
- users.add(new User());
- users.add(new User());
- users.add(new User());
- }
-
- 。。。
-
- }
- @RequestMapping("test.do")
- public void test(UserSetForm userForm) {
- for (User user : userForm.getUsers()) {
- System.out.println(user.getFirstName() + " - " + user.getLastName());
- }
- }
- <</span>form action="test.do" method="post">
- <</span>table>
- <</span>thead>
- <</span>tr>
- <</span>th>First Name</</span>th>
- <</span>th>Last Name</</span>th>
- </</span>tr>
- </</span>thead>
- <</span>tfoot>
- <</span>tr>
- <</span>td colspan="2"><</span>input type="submit" value="Save" /></</span>td>
- </</span>tr>
- </</span>tfoot>
- <</span>tbody>
- <</span>tr>
- <</span>td><</span>input name="users[0].firstName" value="aaa" /></</span>td>
- <</span>td><</span>input name="users[0].lastName" value="bbb" /></</span>td>
- </</span>tr>
- <</span>tr>
- <</span>td><</span>input name="users[1].firstName" value="ccc" /></</span>td>
- <</span>td><</span>input name="users[1].lastName" value="ddd" /></</span>td>
- </</span>tr>
- <</span>tr>
- <</span>td><</span>input name="users[2].firstName" value="eee" /></</span>td>
- <</span>td><</span>input name="users[2].lastName" value="fff" /></</span>td>
- </</span>tr>
- </</span>tbody>
- </</span>table>
- </</span>form>
基本和List绑定类似。需要特别提醒的是,如果最大下标值大于Set的size,则会抛出org.springframework.beans.InvalidPropertyException异常
8、Map绑定:
- public class User {
-
- private String firstName;
-
- private String lastName;
-
- 。。。
-
- }
-
- public class UserMapForm {
-
- private Map users;
-
- 。。。
-
- }
- @RequestMapping("test.do")
- public void test(UserMapForm userForm) {
- for (Map.Entry entry : userForm.getUsers().entrySet()) {
- System.out.println(entry.getKey() + ": " + entry.getValue().getFirstName() + " - " +
- entry.getValue().getLastName());
- }
- }
- <</span>form action="test.do" method="post">
- <</span>table>
- <</span>thead>
- <</span>tr>
- <</span>th>First Name</</span>th>
- <</span>th>Last Name</</span>th>
- </</span>tr>
- </</span>thead>
- <</span>tfoot>
- <</span>tr>
- <</span>td colspan="2"><</span>input type="submit" value="Save" /></</span>td>
- </</span>tr>
- </</span>tfoot>
- <</span>tbody>
- <</span>tr>
- <</span>td><</span>input name="users['x'].firstName" value="aaa" /></</span>td>
- <</span>td><</span>input name="users['x'].lastName" value="bbb" /></</span>td>
- </</span>tr>
- <</span>tr>
- <</span>td><</span>input name="users['y'].firstName" value="ccc" /></</span>td>
- <</span>td><</span>input name="users['y'].lastName" value="ddd" /></</span>td>
- </</span>tr>
- <</span>tr>
- <</span>td><</span>input name="users['z'].firstName" value="eee" /></</span>td>
- <</span>td><</span>input name="users['z'].lastName" value="fff" /></</span>td>
- </</span>tr>
- </</span>tbody>
- </</span>table>
- </</span>form>
最后:
像test(int num)这种把表单字段直接映射到方法参数名的方式是不太靠谱的,这是Spring MVC最大的问题,并且是无法解决的问题,因为它是基于字节码来取方法参数名的,如果在编译源码时不生成debug信息,比如javac -g:none 或者 在eclipse中在Preference那个窗口中选"Java->Compiler"把"Add varible..."那个复选框取消,这样生成的字节码中是不会保存方法参数名的。最靠谱的办法就是基于java源代码来做,或者Spring MVC目前已提供的比较啰嗦的注解方式: 在参数名前加@RequestParam把test(int num)改成下面这样才是万无一失的:
- test(@RequestParam("num") int num)
所以最后在控制器方法上带上这个注解。
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- springMVC对简单对象、Set、List、Map的数据绑定和常见问题.
- springMVC对简单对象、Set、List、Map的数据绑定和常见问题(一)
- springMVC对简单对象、Set、List、Map的数据绑定和常见问题(二)
- springMVC对简单对象、Set、List、Map的数据绑定和常见问题(三)
- springMVC对简单对象、Set、List、Map的数据绑定和常见问题
- springMVC对简单对象、Set、List、Map的数据绑定和常见问题(一)
- springMVC对简单对象、Set、List、Map的数据绑定和常见问题(二)
- springMVC对简单对象、Set、List、Map的数据绑定和常见问题(三)
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