Preface: This article mainly introduces the concepts and usage of data formatting in the data binding process of SpringMVC .
This article focuses on the following issues:
- SpringMVC's Data Formatting Architecture
-
Spring's built-in format converter
- custom format converter
1. SpringMVC's data formatting architecture
1.1 Format Converter
Provides implementation support for format conversion, and formats the input/output of attribute objects, which in essence still belongs to the category of "type conversion".
There are two groups of four interfaces as follows:
1. Printer interface
Format display interface, print and display the T type object in a certain format according to the Locale information (that is, return the string form);
@FunctionalInterface public interface Printer<T> { String print(T object, Locale locale); }
2. Parser interface
Parse the interface, and parse the string into an object of type T according to the Locale information. If the parsing fails, a java.text.ParseException or IllegalArgumentException can be thrown.
@FunctionalInterface public interface Parser<T> { T parse(String text, Locale locale) throws ParseException; }
3. Formatter interface
Format the SPI interface, inherit the Printer and Parser interfaces, and complete the formatting and parsing functions of T type objects;
public interface Formatter<T> extends Printer<T>, Parser<T> { }
4. AnnotationFormatterFactory interface
Annotation-driven field formatting factory for creating Printer and Parser for annotated object fields, that is, for formatting and parsing annotated object fields .
public interface AnnotationFormatterFactory<A extends Annotation> { // Recognized annotation types Set<Class<?>> getFieldTypes(); // A collection of field types that can be type-annotated by A Printer<?> getPrinter(A annotation, Class<?> fieldType); // Get Printer according to A annotation type and fieldType type Parser<?> getParser(A annotation, Class<?> fieldType); // Get Parser according to A annotation type and fieldType type }
This interface returns Printer and Parser for formatting and parsing field values annotated by A-annotated types. For example, JodaDateTimeFormatAnnotationFormatterFactory can create corresponding Printer and Parser for the java.util.Date field type annotated with @DateTimeFormat for formatting and parsing.
1.2 Format Converter Registrar, Format Service
Provides type converter registration support, runtime type conversion API support.
It has two interfaces:
1.FormatterRegistry
Format converter registrar for registering format converters (Formatter, Printer and Parser, AnnotationFormatterFactory);
public interface FormatterRegistry extends ConverterRegistry { // 添加格式化转换器(Spring3.1 新增API) void addFormatter(Formatter<?> formatter); // 为指定的字段类型添加格式化转换器 void addFormatterForFieldType(Class<?> fieldType, Formatter<?> formatter); // 为指定的字段类型添加Printer 和Parser void addFormatterForFieldType(Class<?> fieldType, Printer<?> printer, Parser<?> parser); // 添加注解驱动的字段格式化工厂AnnotationFormatterFactory void addFormatterForFieldAnnotation(AnnotationFormatterFactory<? extends Annotation> annotationFormatterFactory); }
2. FormattingConversionService
继承自ConversionService,运行时类型转换和格式化服务接口,提供运行期类型转换和格式化的支持。该实现类扩展了 GenericConversionService,因此它既具有类型转换的功能,又具有格式化的功能。FormattingConversionService 拥有一个FormattingConversionServiceFactroyBean 工厂类,后者用于在 Spring 上下文中构造前者。
FormattingConversionService内部实现如下图所示:
FormattingConversionService内部实现如上所示,当调用convert方法时:
- 若是S类型----->String:调用私有的静态内部类PrinterConverter,其又调用相应的Printer 的实现进行格式化;
- 若是String----->T类型:调用私有的静态内部类ParserConverter,其又调用相应的Parser 的实现进行解析;
-
若是A 注解类型注解的S 类型----->String:调用私有的静态内部类AnnotationPrinterConverter,其又调用相应的AnnotationFormatterFactory的getPrinter 获取Printer 的实现进行格式化;
-
若是String----->A 注解类型注解的T 类型:调用私有的静态内部类AnnotationParserConverter,其又调用相应的AnnotationFormatterFactory的getParser 获取Parser 的实现进行解析。
注:S类型表示源类型,T类型表示目标类型,A表示注解类型。
此处可以可以看出之前的Converter SPI 完成任意Object 与Object 之间的类型转换,而Formatter SPI 完成任意Object与String之间的类型转换。
2. Spring内建的格式化转换器
类名 |
说明 |
DateFormatter |
java.util.Date<---->String(实现日期的格式化/解析) |
NumberFormatter |
java.lang.Number<---->String(实现通用样式的格式化/解析) |
CurrencyFormatter |
java.lang.BigDecimal<---->String(实现货币样式的格式化/解析) |
PercentFormatter |
java.lang.Number<---->String(实现百分数样式的格式化/解析) |
NumberFormatAnnotationFormatterFactory |
@NumberFormat注解类型的数字字段类型<---->String ①通过@NumberFormat指定格式化/解析格式 ②可以格式化/解析的数字类型:Short、Integer、Long、Float、Double、BigDecimal、BigInteger |
JodaDateTimeFormatAnnotationFormatterFactory |
@DateTimeFormat注解类型的日期字段类型<---->String |
FormattingConversionServiceFactroyBean内部已经注册了NumberFormatAnnotationFormatterFactroy,JodaDateTimeFormatAnnotationFormatterFactroy。
3. 自定义格式转换器
此处以解析/格式化AddressVo为例。字符串"江苏-南京" 格式化为 AddressVo:
1. 定义Formatter实现
public class AddressFormatter_ implements Formatter<AddressVo> { // 中文正则表达式 Pattern pattern = Pattern.compile("^([\u4e00-\u9fa5]*)-([\u4e00-\u9fa5]*)$"); @Override public String print(AddressVo address, Locale locale) { if(address == null) return ""; return new StringBuilder().append(address.getProvince()) .append("-") .append(address.getCity()) .toString(); } @Override public AddressVo parse(String text, Locale locale) throws ParseException { if(!StringUtils.hasLength(text)) return null; Matcher matcher = pattern.matcher(text); if(matcher.matches()) { String province = matcher.group(1); String city = matcher.group(2); return new AddressVo(province, city); } else { throw new IllegalArgumentException(); } } }
2. 定义解析/格式化字段的注解类型
@Target({ElementType.METHOD, ElementType.FIELD, ElementType.PARAMETER}) @Retention(RetentionPolicy.RUNTIME) public @interface AddressFormatter { }
3. 实现AnnotationFormatterFactory注解格式化工厂
public class AddressFormatAnnotationFormatterFactory implements AnnotationFormatterFactory<AddressFormatter> { private final AddressFormatter_ formatter; public AddressFormatAnnotationFormatterFactory() { this.formatter = new AddressFormatter_(); } //②指定可以被解析/格式化的字段类型集合 @Override public Set<Class<?>> getFieldTypes() { Set<Class<?>> set = new HashSet<Class<?>>(); set.add(AddressVo.class); return set; } @Override public Parser<?> getParser(AddressFormatter annotation, Class<?> fieldType) { return formatter; } @Override public Printer<?> getPrinter(AddressFormatter annotation, Class<?> fieldType) { return formatter; } }
4. 对实体类添加注解
@AddressFormatter private AddressVo address;
5. 注册自定义转换器
<!-- 配置 ConversionService --> <bean id="conversionService" class="org.springframework.format.support.FormattingConversionServiceFactoryBean"> <property name="formatters"> <set> <bean class="com.wj.web.formatters.AddressFormatAnnotationFormatterFactory"></bean> </set> </property> </bean>
4. 简述Spring內建常用格式化注解用法
1.@DateTimeFormat
@DateTimeFormat 注解可对java.util.Date、java.util.Calendar、java.long.Long 时间类型进行标注:
- pattern 属性:类型为字符串。指定解析/格式化字段数据的模式,如:”yyyy-MM-dd hh:mm:ss”;
- iso 属性:类型为 DateTimeFormat.ISO。指定解析/格式化字段数据的ISO模式,包括四种:ISO.NONE(不使用) 默认、ISO.DATE(yyyy-MM-dd) 、ISO.TIME(hh:mm:ss.SSSZ)、ISO.DATE_TIME(yyyy-MM-dd hh:mm:ss.SSSZ);
- style 属性:字符串类型。通过样式指定日期时间的格式,由两位字符组成,第一位表示日期的格式,第二位表示时间的格式:S:短日期/时间格式、M:中日期/时间格式、L:长日期/时间格式、F:完整日期/时间格式、-:忽略日期或时间格式;
2. @NumberFormat
可对类似数字类型的属性进行标注,它拥有两个互斥的属性:
- style:类型为 NumberFormat.Style。用于指定– 样式类型,包括三种:Style.NUMBER(正常数字类型)、Style.CURRENCY(货币类型)、 Style.PERCENT(百分数类型);
- pattern:类型为 String,自定义样式, 如patter="#,###";
3. 示例
@NumberFormat(pattern="#,####,####.#") private double salary; @DateTimeFormat(pattern="yyyy-MM-dd") private Date birth;
代码下载来源:http://super-wangj.iteye.com/blog/2388430