优化网站技术,做搜狗网站点,企业网页设计费用,网站后台更新图片一、思考
假设给一个java bean#xff0c;让你按照 json 的格式打印出来#xff0c;你会怎么做#xff1f; 比如这个java bean 长这样#xff0c;并且创建了一个叫宝儿姐的朋友
package com.test;public class User {private String name;private Integer age;private Bi…一、思考
假设给一个java bean让你按照 json 的格式打印出来你会怎么做 比如这个java bean 长这样并且创建了一个叫宝儿姐的朋友
package com.test;public class User {private String name;private Integer age;private BigDecimal mony;private ListUser childs;public String getName() {return name;}public void setName(String name) {this.name name;}public Integer getAge() {return age;}public void setAge(Integer age) {this.age age;}public BigDecimal getMony() {return mony;}public void setMony(BigDecimal mony) {this.mony mony;}public ListUser getChilds() {return childs;}public void setChilds(ListUser childs) {this.childs childs;}
}public class JsonTest {public static void main(String[] args) throws Exception {User user new User();user.setAge(18);user.setName(宝儿姐);user.setMony(new BigDecimal(-4000000.5));ListUser userList new ArrayList();User son new User();son.setAge(1);son.setName(大壮);userList.add(son);User daughter new User();daughter.setAge(10);daughter.setName(小美);userList.add(daughter);user.setChilds(userList);// 打印java beanprintToJson(user);// 打印集合printToJson(userList);// 打印数值printToJson(new BigDecimal(1.235));printToJson((byte)2);printToJson((short)3);printToJson(4);printToJson(5.1F);printToJson(5.2D);printToJson(233L);// 打印字符串printToJson(小美);}private static void printToJson(User user) {// .....}
}
我们调用 printToJson 之后期望的输出是长这样的
{name:宝儿姐,childs:[{name:大壮,age:1},{name:小美,age:10}],age:18,mony:-4000000.5}
[{name:大壮,age:1},{name:小美,age:10}]
1.235
2
3
4
5.1
5.2
233
小美那么一个简单而又没啥设计的实现方式如下
public class JsonTest {public static void main(String[] args) throws Exception {User user new User();user.setAge(18);user.setName(宝儿姐);user.setMony(new BigDecimal(-4000000.5));ListUser userList new ArrayList();User son new User();son.setAge(1);son.setName(大壮);userList.add(son);User daughter new User();daughter.setAge(10);daughter.setName(小美);userList.add(daughter);user.setChilds(userList);// 打印java beanprintToJson(user);// 打印集合printToJson(userList);// 打印数值printToJson(new BigDecimal(1.235));printToJson((byte)2);printToJson((short)3);printToJson(4);printToJson(5.1F);printToJson(5.2D);printToJson(233L);// 打印字符串printToJson(小美);}private static T void printToJson(T obj) throws Exception {if (Objects.isNull(obj)) {System.out.println();return;}Class? tClass obj.getClass();StringWriter stringWriter new StringWriter();if (tClass String.class) {stringPrint(stringWriter, (String) obj);} else if (Number.class.isAssignableFrom(tClass)) {numberPrint(stringWriter, (Number) obj);} else if (Collection.class.isAssignableFrom(tClass)) {collectionPrint(stringWriter, (Collection) obj, null);// 省略数组map等各种类型的打印} else {javaBeanPrint(stringWriter, obj, tClass);}System.out.println(stringWriter.toString());}private static void javaBeanPrint(StringWriter stringWriter, Object javaBean, Class? tClass) throws Exception {// 不考虑继承Method[] methods tClass.getDeclaredMethods();if (Objects.isNull(methods) || methods.length 0) {stringWriter.append({});return;}stringWriter.append({);boolean hasPrev false;for (Method method : methods) {String methodName method.getName();if (methodName.startsWith(get) methodName.length() 3) {Object val method.invoke(javaBean);if (Objects.isNull(val)) {continue;}if (hasPrev) {stringWriter.append(,);}String propertyName methodName.substring(3);String newPropertyName;if (propertyName.length() 1) {newPropertyName propertyName.substring(0, 1).toLowerCase() propertyName.substring(1);} else {newPropertyName propertyName.substring(0, 1).toLowerCase();}stringWriter.append(\).append(newPropertyName).append(\).append(:);Class? returnType method.getReturnType();if (returnType String.class) {stringPrint(stringWriter, (String) val);} else if (Number.class.isAssignableFrom(returnType)) {numberPrint(stringWriter, (Number) val);} else if (Collection.class.isAssignableFrom(returnType)) {Type type method.getGenericReturnType();collectionPrint(stringWriter, (Collection) val, type);// 省略数组map等各种类型的打印} else {javaBeanPrint(stringWriter, val, val.getClass());}hasPrev true;}}stringWriter.append(});}private static void stringPrint(StringWriter stringWriter, String val) {stringWriter.append(\).append(val).append(\);}private static void numberPrint(StringWriter stringWriter, Number val) {if (val instanceof BigDecimal) {stringWriter.append(((BigDecimal) val).toPlainString());} else {stringWriter.append(val.toString());}}private static void collectionPrint(StringWriter stringWriter, Collection val, Type type) throws Exception {if(Objects.isNull(val) || val.size() 0) {stringWriter.append([]);return;}stringWriter.append([);boolean havPrev false;for (Object v : val) {if(Objects.isNull(v)) {continue;}if(havPrev) {stringWriter.append(,);}Class? vClass v.getClass();if (vClass String.class) {stringPrint(stringWriter, (String) v);} else if (Number.class.isAssignableFrom(vClass)) {numberPrint(stringWriter, (Number) v);} else if (Collection.class.isAssignableFrom(vClass)) {collectionPrint(stringWriter, (Collection) v, type);// 省略数组map等各种类型的打印} else {javaBeanPrint(stringWriter, v, vClass);}havPrev true;}stringWriter.append(]);}
}以上是一个非常简单的实现我们可以看到针对每种数据类型它的序列化方式是不一样的所以其实 我们可以使用策略模式加以改造比如定义一个接口加一个参数上下文根据不同的数据类型实现 不同的序列化器。
