常用JSON工具类JsonUtil封装

前言

Maven依赖

<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-mapper-asl</artifactId>
<version>1.9.13</version>
</dependency>

如果项目没有使用Maven可以直接下载jar包

↓↓↓

package com.suddev.util;

import org.apache.commons.lang3.StringUtils;
import org.codehaus.jackson.map.DeserializationConfig;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializationConfig;
import org.codehaus.jackson.map.annotate.JsonSerialize.Inclusion;
import org.codehaus.jackson.type.JavaType;
import org.codehaus.jackson.type.TypeReference;

import java.io.IOException;
import java.text.SimpleDateFormat;

/**
* Jackson工具类
*
* @author suddev
* @create 2017-11-25 2:18 PM
**/
public class JsonUtil1 {

private static ObjectMapper objectMapper = new ObjectMapper();

static {
// 对象字段全部列入
objectMapper.setSerializationInclusion(Inclusion.NON_DEFAULT);

// 取消默认转换timestamps形式
objectMapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS,false);

// 忽略空bean转json的错误
objectMapper.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS,false);

// 统一日期格式yyyy-MM-dd HH:mm:ss
objectMapper.setDateFormat(new SimpleDateFormat(DateTimeUtil.STANDARD_FORMAT));

// 忽略在json字符串中存在,但是在java对象中不存在对应属性的情况
objectMapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES,false);
}

/**
* Object转json字符串
* @param obj
* @param <T>
* @return
*/
public static <T> String obj2String(T obj){
if (obj == null){
return null;
}
try {
return obj instanceof String ? (String) obj : objectMapper.writeValueAsString(obj);
} catch (Exception e) {
System.out.println("Parse object to String error");
e.printStackTrace();
return null;
}
}

/**
* Object转json字符串并格式化美化
* @param obj
* @param <T>
* @return
*/
public static <T> String obj2StringPretty(T obj){
if (obj == null){
return null;
}
try {
return obj instanceof String ? (String) obj : objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj);
} catch (Exception e) {
System.out.println("Parse object to String error");
e.printStackTrace();
return null;
}
}

/**
* string转object
* @param str json字符串
* @param clazz 被转对象class
* @param <T>
* @return
*/
public static <T> T string2Obj(String str,Class<T> clazz){
if (StringUtils.isEmpty(str) || clazz == null){
return null;
}
try {
return clazz.equals(String.class)? (T) str :objectMapper.readValue(str,clazz);
} catch (IOException e) {
System.out.println("Parse String to Object error");
e.printStackTrace();
return null;
}
}

/**
* string转object
* @param str json字符串
* @param typeReference 被转对象引用类型
* @param <T>
* @return
*/
public static <T> T string2Obj(String str, TypeReference<T> typeReference){
if (StringUtils.isEmpty(str) || typeReference == null){
return null;
}
try {
return (T)(typeReference.getType().equals(String.class)? str :objectMapper.readValue(str,typeReference));
} catch (IOException e) {
System.out.println("Parse String to Object error");
e.printStackTrace();
return null;
}
}

/**
* string转object 用于转为集合对象
* @param str json字符串
* @param collectionClass 被转集合class
* @param elementClasses 被转集合中对象类型class
* @param <T>
* @return
*/
public static <T> T string2Obj(String str,Class<?> collectionClass,Class<?>... elementClasses){
JavaType javaType = objectMapper.getTypeFactory().constructParametricType(collectionClass,elementClasses);
try {
return objectMapper.readValue(str,javaType);
} catch (IOException e) {
System.out.println("Parse String to Object error");
e.printStackTrace();
return null;
}
}
}

测试代码

case1 obj转json

public static void main(String[] args) {
User user = new User();
user.setUsername("suddev");
user.setId(123);
String s = JsonUtil.obj2String(user);
System.out.println(s);
}

case2 输出美化后的json字符串

public static void main(String[] args) {
User user = new User();
user.setUsername("suddev");
user.setId(123);
String s = JsonUtil1.obj2StringPretty(user);
System.out.println(s);
}

case3 json字符串转obj

public static void main(String[] args) {
String s = "{\"id\":123,\"username\":\"suddev\"}";
User user = JsonUtil.string2Obj(s,User.class);
}

case4 使用TypeReference转换复杂对象

public static void main(String[] args) {
User u1 = new User();
u1.setUsername("aaa");u1.setId(1);
User u2 = new User();
u2.setUsername("bbb");u2.setId(2);
List<User> userList = Lists.newArrayList();
userList.add(u1);userList.add(u2);
String userListStr = JsonUtil.obj2StringPretty(userList);
List<User> userListObj = JsonUtil.string2Obj(userListStr, new TypeReference<List<User>>() {});
}

case5 更简单直接的复杂对象转换方法

public static void main(String[] args) {
User u1 = new User();
u1.setUsername("aaa");u1.setId(1);
User u2 = new User();
u2.setUsername("bbb");u2.setId(2);
List<User> userList = Lists.newArrayList();
userList.add(u1);userList.add(u2);
String userListStr = JsonUtil.obj2StringPretty(userList);
// List<User> userListObj = JsonUtil.string2Obj(userListStr, new TypeReference<List<User>>() {});
// 依次传入集合以及集合中对象类型的class
List<User> userListObj2 = JsonUtil.string2Obj(userListStr,List.class,User.class);
}

方便项目中使用将System.out替换为log的版本

/**
* Jackson工具类
*
* @author suddev
* @create 2017-11-25 2:18 PM
**/
@Slf4j
public class JsonUtil {

private static ObjectMapper objectMapper = new ObjectMapper();

static {
// 对象字段全部列入
objectMapper.setSerializationInclusion(Inclusion.NON_DEFAULT);

// 取消默认转换timestamps形式
objectMapper.configure(SerializationConfig.Feature.WRITE_DATES_AS_TIMESTAMPS,false);

// 忽略空bean转json的错误
objectMapper.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS,false);

// 统一日期格式yyyy-MM-dd HH:mm:ss
objectMapper.setDateFormat(new SimpleDateFormat(DateTimeUtil.STANDARD_FORMAT));

// 忽略在json字符串中存在,但是在java对象中不存在对应属性的情况
objectMapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES,false);
}

public static <T> String obj2String(T obj){
if (obj == null){
return null;
}
try {
return obj instanceof String ? (String) obj : objectMapper.writeValueAsString(obj);
} catch (Exception e) {
log.warn("Parse object to String error",e);
return null;
}
}

public static <T> String obj2StringPretty(T obj){
if (obj == null){
return null;
}
try {
return obj instanceof String ? (String) obj : objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj);
} catch (Exception e) {
log.warn("Parse object to String error",e);
return null;
}
}

public static <T> T string2Obj(String str,Class<T> clazz){
if (StringUtils.isEmpty(str) || clazz == null){
return null;
}
try {
return clazz.equals(String.class)? (T) str :objectMapper.readValue(str,clazz);
} catch (IOException e) {
log.warn("Parse String to Object error",e);
return null;
}
}

public static <T> T string2Obj(String str, TypeReference<T> typeReference){
if (StringUtils.isEmpty(str) || typeReference == null){
return null;
}
try {
return (T)(typeReference.getType().equals(String.class)? str :objectMapper.readValue(str,typeReference));
} catch (IOException e) {
log.warn("Parse String to Object error",e);
return null;
}
}

public static <T> T string2Obj(String str,Class<?> collectionClass,Class<?>... elementClasses){
JavaType javaType = objectMapper.getTypeFactory().constructParametricType(collectionClass,elementClasses);
try {
return objectMapper.readValue(str,javaType);
} catch (IOException e) {
log.warn("Parse String to Object error",e);
return null;
}
}
}