Spring MVC 之数据绑定
数据绑定是将用户输入绑定到领域模型的一种特性。
Http 请求传递的数据为 String 类型,通过数据绑定,可以将数据填充为不同类型的对象属性。
基本类型绑定
@RequestMapping("/int")
@ResponseBody
public String bindInt (int i) {
return "bindInt:" + i;
}
请求:/int?i=10
响应:bindInt:3
错误请求:/int or /int?2
错误代码:500
基本类型数据绑定时,必须传入key
和value
。
包装类型绑定
@RequestMapping("/integer")
@ResponseBody
public String bindInteger (Integer i) {
return "bindInteger:" + i;
}
请求:/integer?i=5
响应:bindInteger:5
请求:/integer or /integer?5 or /integer?i or /integer?i=
响应:bindInteger:null
包装类型数据绑定时,key
和value
均可为空。
若要求必须传入参数,可加@RequestParam
。
@RequestMapping("/integer")
@ResponseBody
public String bindInteger (@RequestParam Integer i) {
return "bindInteger:" + i;
}
错误请求:/integer or /integer?5
错误代码:400
请求:/integer?i or /integer?i=
响应:bindInteger:null
数组绑定
@RequestMapping("/array")
@ResponseBody
public String bindArray (String[] strs) {
StringBuilder sb = new StringBuilder();
sb.append("bindArray:");
for (String str : strs)
sb.append(str + " ");
return sb.toString();
}
请求:/array?strs=str1&strs=str2
响应:bindArray:str1 str2
简单对象绑定
@RequestMapping("/user")
@ResponseBody
public String bindUser (User user) {
return "bindUser:" + user.toString();
}
public class User {
private String name;
private Integer age;
// getters and setters
// toString
}
请求:/user?name=Tom&age=15
响应:bindUser:User [name=Tom, age=15]
多层级对象绑定
public class User {
private String name;
private Integer age;
private ContactInfo info;
// getters and setters
// toString
}
public class ContactInfo {
private String phone;
private String address;
// getters and setters
// toString
}
请求:/user?name=Tom&info.phone=123456
响应:bindUser:User [name=Tom, age=null, info=ContactInfo [phone=123456, address=null]]
同属性多对象绑定
@RequestMapping("/userandadmin")
@ResponseBody
public String bindUserAndAdmin (User user, Admin admin) {
return "bindUserAndAdmin:
" + user.toString() + "
" + admin.toString();
}
public class Admin {
private String name;
private Integer age;
// getters and setters
// toString
}
请求:/userandadmin?name=Tom&age=15
响应:
bindUserAndAdmin:
User [name=Tom, age=15]
Admin [name=Tom, age=15]
数据同时被绑定到了具有相同属性的两个对象上。
解决方式:
@InitBinder("user")
public void initUser(WebDataBinder binder) {
binder.setFieldDefaultPrefix("user.");
}
@InitBinder("admin")
public void initAdmin(WebDataBinder binder) {
binder.setFieldDefaultPrefix("admin.");
}
请求:/userandadmin?user.name=Tom&age=15&admin.name=Jack
响应:
bindUserAndAdmin:
User [name=Tom, age=15]
Admin [name=Jack, age=15]
InitBinder
作用在该控制器中,进入控制器后先调用InitBinder
后调用RequestMapping
方法。
不配置InitBinder
加前缀无效,不能成功绑定。
WebDataBinder
用来绑定请求参数到指定JavaBean
。
List 绑定
@RequestMapping("/stringlist")
@ResponseBody
public String bindStringList (@RequestParam("name") List<String> strs) {
return "bindStringList:" + strs.toString();
}
请求:/stringlist?name=Tom&name=Jack
响应:bindStringList:[Tom, Jack]
@RequestMapping("/userlist")
@ResponseBody
public String bindUserList(UserListForm userListForm){
return "bindUserList:
" + usersModel.toString();
}
public class UserListForm {
private List<User> list;
// getters and setters
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
for (User u : users)
sb.append(u.toString() + "
");
return sb.toString();
}
}
请求:/userlist?users[0].name=Tom&users[2].name=Jack
响应:
bindList:
User [name=Tom, age=null]
User [name=null, age=null]
User [name=Jack, age=null]
PS:tomcat 高版本中[
需要转义为%5B
,]
需要转义为%5D
Set 绑定
Set 与 List 绑定基本一致,但在使用Set<User>
时,需先初始化Set的容量。
public class UserSetForm {
private Set<User> users;
private UserSetForm () {
// 设置 set 容量为 2 不能访问 size 外的对象
// 如果覆盖了 User 的 equals 和 hashcode 方法 则 set 容量为 1
users = new HashSet<User>();
users.add(new User());
users.add(new User());
System.out.println(users.size());
}
// getters and setters
// toString
}
// User.java
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((age == null) ? 0 : age.hashCode());
result = prime * result + ((name == null) ? 0 : name.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
User other = (User) obj;
if (age == null) {
if (other.age != null)
return false;
} else if (!age.equals(other.age))
return false;
if (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
return true;
}
请求:/userset?users[0].name=Tom
响应:
bindUserSet:
User [name=Tom, age=null]
错误请求:/userset?users[0].name=Tom&users[1].name=Jack
错误代码:500
错误说明:Cannot get element with index 1 from Set of size 1, accessed using property path 'users[1]'
Map 绑定
@RequestMapping("/usermap")
@ResponseBody
public String bindUserMap (UserMapForm userMapForm) {
return "bindUserMap:
" + userMapForm.toString();
}
public class UserMapForm {
private Map<String, User> users;
// getters and setters
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
for (String s : users.keySet())
sb.append("Users[" + s + "] = " + users.get(s) + "
");
return sb.toString();
}
}
请求:/usermap?users[x].name=Tom&users[y].name=Jack
响应:
bindUserMap:
Users[x] = User [name=Tom, age=null]
Users[y] = User [name=Jack, age=null]
JSON 绑定
@RequestMapping("/userjson")
@ResponseBody
public String bindUserJson (@RequestBody User user) {
return "bindUserJson:" + user.toString();
}
请求:
Content-Type:application/json
Body:
{
"name":"Tom",
"age":15
}
响应:bindUserJson:User [name=Tom, age=15]
依赖:jackson-databind
XML 绑定
@RequestMapping("/userxml")
@ResponseBody
public String bindUserXml (@RequestBody User user) {
return "bindUserXml:" + user.toString();
}
@XmlRootElement(name="user")
public class User {
private String name;
private Integer age;
@XmlElement(name="name")
public String getName() {
return name;
}
@XmlElement(name="age")
public Integer getAge() {
return age;
}
// setters
// toString
}
请求:
Content-Type:application/xml
Body:
<user>
<name>Tom</name>
<age>15</age>
</user>
响应:bindUserXml:User [name=Tom, age=15]
依赖:jaxb-api jaxb-impl spring-oxm
PropertyEditor
public interface PropertyEditor {
void setValue(Object value);
Object getValue();
String getAsText();
void setAsText(String text) throws java.lang.IllegalArgumentException;
// ...
}
使用:一般使用内置或继承PropertyEditorSupport(implements PropertyEditor)
,配合WebDataBinder
局部使用。
@RequestMapping("/datepe")
@ResponseBody
public String bindDateByPropertyEditor (Date date1) {
return date1.toString();
}
@InitBinder("date1")
public void initDate (WebDataBinder binder) {
binder.registerCustomEditor(Date.class, new CustomDateEditor(new SimpleDateFormat("yyyy-MM-dd"), true));
}
请求:/datepe?date1=2019-11-11
响应:Mon Nov 11 00:00:00 CST 2019
Formatter
public interface Formatter<T> extends Printer<T>, Parser<T> {
}
public interface Printer<T> {
String print(T object, Locale locale);
}
public interface Parser<T> {
T parse(String text, Locale locale) throws ParseException;
}
使用:Source 为 String 类型,可全局或局部使用。
@RequestMapping("/dateformatter")
@ResponseBody
public String bindDateByFormatter (Date date2) {
return date2.toString();
}
<mvc:annotation-driven conversion-service="formatter"/>
<!-- conversion-service 与 id 对应 -->
<bean id="formatter" class="org.springframework.format.support.FormattingConversionServiceFactoryBean">
<property name="formatters">
<set>
<bean class="org.springframework.format.datetime.DateFormatter">
<constructor-arg name="pattern" value="yyyy-MM-dd" />
</bean>
</set>
</property>
</bean>
请求:/dateformatter?date2=2019-12-12
响应:Thu Dec 12 00:00:00 CST 2019
Converter
public interface Converter<S, T> {
@Nullable
T convert(S source);
}
使用:内置实现为 final 类,不可扩展,可自定义源类型和目的类型,可全局或局部使用。
@RequestMapping("/dateconverter")
@ResponseBody
public String bindDateByConverter (Date date3) {
return date3.toString();
}
public class DateConverter implements Converter<String, Date> {
public Date convert(String source) {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
try {
return format.parse(source);
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}
}
<mvc:annotation-driven conversion-service="converter"/>
<!-- 自定义 Converter 类 -->
<bean id="converter" class="org.springframework.format.support.FormattingConversionServiceFactoryBean">
<property name="converters">
<set>
<bean class="common.DateConverter" />
</set>
</property>
</bean>
请求:/dateconverter?date3=2019-10-24
响应:Thu Oct 24 00:00:00 CST 2019
参考资料:SpringMVC数据绑定入门