Java处理JSON数据有三个比较流行的类库FastJSON、Gson和Jackson。本文将测试这三个类库在JSON序列化和反序列化的方面表现，主要测试JSON序列化和反序列化的速度。为了防止由于内存导致测试结果出现偏差，测试中对JVM内存配置-Xmx4g -Xms4g。
JSON序列化(Object => JSON)
测试样本数量为100000个，为了保证每个类库在测试中都能处理同一个样本，先把样本Java对象保存在文件中。每个类库测试3次，每次循环测试10遍，去掉最快速度和最慢速度，对剩下的8遍求平均值作为最终的速，取3次测试中最好的平均速度作为最终的测试数据。
| 类库 | 样本数量 | 执行次数 | 最长时间(毫秒) | 最短时间(毫秒) | 平均时间(毫秒) |
|---|---|---|---|---|---|
| FastJSON | 100000 | 10 | 2291.22 | 1416.70 | 1454.93 |
| Jackson | 100000 | 10 | 1980.92 | 841.91 | 880.82 |
| Gson | 100000 | 10 | 2383.02 | 1469.08 | 1520.38 |
从测试数据可知，FastJSON和GsonJSON序列化的速度差不多，Jackson是最快的（用时Gson少大约600毫秒）。
JSON反序列化(JSON => Object)
测试样本数量为100000个，为了保证每个类库在测试中都能处理同一个样本，先把样本JSON对象保存在文件中。每个类库测试3次，每次循环测试10遍，去掉最快速度和最慢速度，对剩下的8遍求平均值作为最终的速，取3次测试中最好的平均速度作为最终的测试数据。
| 类库 | 样本数量 | 执行次数 | 最长时间(毫秒) | 最短时间(毫秒) | 平均时间(毫秒) |
|---|---|---|---|---|---|
| FastJSON | 100000 | 10 | 7942.31 | 6340.55 | 6526.41 |
| Jackson | 100000 | 10 | 7957.22 | 6623.85 | 6815.41 |
| Gson | 100000 | 10 | 8235.15 | 7006.06 | 7364.75 |
从测试数据可知，三个类库在反序列化上性能比较接近，Gson稍微差一些。
总结
把Java对象JSON序列化，Jackson速度最快，在测试中比Gson快接近50%，FastJSON和Gson速度接近。
把JSON反序列化成Java对象，FastJSON、Jackson速度接近，Gson速度稍慢，不过差距很小。
样本对象
样本对象包括Boolean、Int、Long、Double、Date、String、List和Map字段，其中List长度和Map的Key数量可以根据需要改变。
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
/**
* 该类提供生成样本的元数据
* @author accountwcx@qq.com
*
*/
public class DataBuilder {
private static final String[] chars = new String[] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b",
"c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w",
"x", "y", "z", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R",
"S", "T", "U", "V", "W", "X", "Y", "Z" };
private static final int charNum = 62;
// 样本String最大长度
private static final int maxStrLength = 100;
// 样本String默认长度
private static final int defaultStrLength = 50;
// 样本List最大长度
private static final int maxListSize = 100;
// 样本List默认长度
private static final int defaultListSize = 10;
// 样本Map最大Key数量
private static final int maxMapSize = 100;
// 样本Map默认Key数量
private static final int defaultMapSize = 10;
// 样本Map中Value的数据类型
private static final String[] types = new String[] { "boolean", "int", "long", "double", "date", "string"};
private static final int typeNum = 6;
private static final Random random = new Random();
/**
* 生成随机长度的字符串
* @return 字符串
*/
public static String randomString(){
return randomString(random.nextInt(maxStrLength));
}
/**
* 生成指定长度的字符串
* @param len 字符串长度
* @return
*/
public static String randomString(int len) {
if (len < 1 || len > maxStrLength) {
// 如果字符串长度超出范围，使用默认长度
len = defaultStrLength;
}
StringBuilder sb = new StringBuilder(len);
for (int i = 0; i < len; i++) {
sb.append(chars[random.nextInt(charNum)]);
}
return sb.toString();
}
/**
* 生成List样本，List中元素的数量随机
* @return
*/
public static List<String> randomStringList() {
return randomStringList(random.nextInt(maxListSize));
}
/**
* 生成List样本
* @param size List中元素的数量
* @return
*/
public static List<String> randomStringList(int size) {
if (size < 1 || size > maxListSize) {
size = defaultListSize;
}
List<String> list = new ArrayList<String>();
for (int i = 0; i < size; i++) {
list.add(randomString(random.nextInt(maxStrLength)));
}
return list;
}
/**
* 生成随机Map样本，样本中key的数量随机
* @return
*/
public static Map<String, Object> randomMap() {
return randomMap(random.nextInt(maxMapSize));
}
/**
* 生成随机Map样本
* @param size 样本中key的数量
* @return
*/
public static Map<String, Object> randomMap(int size) {
if (size < 1 || size > maxMapSize) {
size = defaultMapSize;
}
Map<String, Object> map = new HashMap<String, Object>();
for (int i = 0; i < size; i++) {
String type = types[random.nextInt(typeNum)];
if ("boolean".equals(type)) {
map.put("key" + i, random.nextBoolean());
} else if ("int".equals(type)) {
map.put("key" + i, random.nextInt());
} else if ("long".equals(type)) {
map.put("key" + i, random.nextLong());
} else if ("double".equals(type)) {
map.put("key" + i, random.nextDouble());
} else if ("date".equals(type)) {
map.put("key" + i, new Date());
} else if ("string".equals(type)) {
map.put("key" + i, randomString(random.nextInt(maxStrLength)));
}
}
return map;
}
}import java.io.Serializable;
import java.util.Date;
import java.util.List;
import java.util.Map;
import java.util.Random;
/**
* 样本对象
* @author accountwcx@qq.com
*
*/
public class SampleEntity implements Serializable {
private static final long serialVersionUID = -1520171788566678009L;
private Boolean fieldBoolean;
private Integer fieldInt;
private Long fieldLong;
private Double fieldDouble;
private Date fieldDate;
private String fieldStr;
private List<String> fieldList;
private Map<String, Object> fieldMap;
/**
* 随机样本
*/
public SampleEntity() {
Random random = new Random();
fieldBoolean = random.nextBoolean();
fieldInt = random.nextInt();
fieldLong = random.nextLong();
fieldDouble = random.nextDouble();
fieldDate = new Date();
fieldStr = DataBuilder.randomString();
fieldList = DataBuilder.randomStringList();
fieldMap = DataBuilder.randomMap();
}
/**
* 指定List元素数量和Map元素数量的样本
* @param listSize List元素数量
* @param mapKeyNum Map元素数量
*/
public SampleEntity(int listSize, int mapKeyNum) {
Random random = new Random();
fieldBoolean = random.nextBoolean();
fieldInt = random.nextInt();
fieldLong = random.nextLong();
fieldDouble = random.nextDouble();
fieldDate = new Date();
fieldStr = DataBuilder.randomString();
fieldList = DataBuilder.randomStringList(listSize);
fieldMap = DataBuilder.randomMap(mapKeyNum);
}
public Boolean getFieldBoolean() {
return fieldBoolean;
}
public void setFieldBoolean(Boolean fieldBoolean) {
this.fieldBoolean = fieldBoolean;
}
public Integer getFieldInt() {
return fieldInt;
}
public void setFieldInt(Integer fieldInt) {
this.fieldInt = fieldInt;
}
public Long getFieldLong() {
return fieldLong;
}
public void setFieldLong(Long fieldLong) {
this.fieldLong = fieldLong;
}
public Double getFieldDouble() {
return fieldDouble;
}
public void setFieldDouble(Double fieldDouble) {
this.fieldDouble = fieldDouble;
}
public Date getFieldDate() {
return fieldDate;
}
public void setFieldDate(Date fieldDate) {
this.fieldDate = fieldDate;
}
public String getFieldStr() {
return fieldStr;
}
public void setFieldStr(String fieldStr) {
this.fieldStr = fieldStr;
}
public List<String> getFieldList() {
return fieldList;
}
public void setFieldList(List<String> fieldList) {
this.fieldList = fieldList;
}
public Map<String, Object> getFieldMap() {
return fieldMap;
}
public void setFieldMap(Map<String, Object> fieldMap) {
this.fieldMap = fieldMap;
}
}import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.LinkedList;
import java.util.List;
import com.alibaba.fastjson.JSON;
/**
* 创建样本
* @author accountwcx@qq.com
*
*/
public class SampleBuilder {
public static void main(String[] args) {
int sampleSize = 100000;
String jsonDataPath = "d:\\samples_json.dat";
String objectDataPath = "d:\\samples_object.dat";
buildJsonSamples(sampleSize, 10, 10, jsonDataPath);
buildObjectSamples(sampleSize, 10, 10, objectDataPath);
}
public static List<String> loadJSONSamples(String filePath) {
List<String> list = new LinkedList<String>();
File file = new File(filePath);
if (!file.exists()) {
return list;
}
BufferedReader br = null;
try {
br = new BufferedReader(new FileReader(file));
String line = br.readLine();
while(line != null){
list.add(line);
line = br.readLine();
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (null != br) {
try {
br.close();
} catch (IOException e) {
}
}
}
return list;
}
@SuppressWarnings("unchecked")
public static List<SampleEntity> loadSamples(String filePath) {
List<SampleEntity> list = new LinkedList<SampleEntity>();
File file = new File(filePath);
if (!file.exists()) {
return list;
}
ObjectInputStream ois = null;
try {
ois = new ObjectInputStream(new FileInputStream(file));
list = (List<SampleEntity>) ois.readObject();
} catch (Exception e) {
e.printStackTrace();
} finally {
if (null != ois) {
try {
ois.close();
} catch (IOException e) {
}
}
}
return list;
}
/**
* 创建样本
*
* @param sampleSize 样本数量
* @param listSize 样本List长度
* @param mapKeyNum 样本Map的Key数量
* @return 样本List
*/
public static List<SampleEntity> buildSamples(int sampleSize, int listSize, int mapKeyNum) {
List<SampleEntity> list = new LinkedList<SampleEntity>();
for (int i = 0; i < sampleSize; i++) {
list.add(new SampleEntity(listSize, mapKeyNum));
}
return list;
}
/**
* 用默认参数创建样本，其中listSize默认为10，mapKeyNum默认为10。
*
* @param sampleSize
* @return 样本List
*/
public static List<SampleEntity> buildSamples(int sampleSize) {
List<SampleEntity> list = new LinkedList<SampleEntity>();
for (int i = 0; i < sampleSize; i++) {
list.add(new SampleEntity());
}
return list;
}
/**
* 创建样本，并把样本JSON序列化，保存到文件中。
*
* @param sampleSize 样本数量
* @param listSize 样本List长度
* @param mapKeyNum 样本Map中Key的数量
* @param filePath 样本输出的文件路径
*/
public static void buildJsonSamples(int sampleSize, int listSize, int mapKeyNum, String filePath) {
File file = new File(filePath);
File parent = file.getParentFile();
if (!parent.exists()) {
parent.mkdirs();
}
if (file.exists()) {
file.delete();
}
List<SampleEntity> list = buildSamples(sampleSize, listSize, mapKeyNum);
StringBuilder sb = new StringBuilder();
for (SampleEntity item : list) {
sb.append(JSON.toJSONString(item));
sb.append("\n");
}
BufferedWriter bw = null;
try {
file.createNewFile();
bw = new BufferedWriter(new FileWriter(file));
bw.write(sb.toString());
bw.flush();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (null != bw) {
try {
bw.close();
} catch (IOException e) {
}
}
}
}
public static void buildJsonSamples(int sampleSize, String filePath) {
File file = new File(filePath);
File parent = file.getParentFile();
if (!parent.exists()) {
parent.mkdirs();
}
if (file.exists()) {
file.delete();
}
List<SampleEntity> list = buildSamples(sampleSize);
StringBuilder sb = new StringBuilder();
for (SampleEntity item : list) {
sb.append(JSON.toJSONString(item));
sb.append("\n");
}
BufferedWriter bw = null;
try {
file.createNewFile();
bw = new BufferedWriter(new FileWriter(file));
bw.write(sb.toString());
bw.flush();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (null != bw) {
try {
bw.close();
} catch (IOException e) {
}
}
}
}
public static void buildObjectSamples(int sampleSize, String filePath) {
List<SampleEntity> list = buildSamples(sampleSize);
File file = new File(filePath);
File parent = file.getParentFile();
if (!parent.exists()) {
parent.mkdirs();
}
if (file.exists()) {
file.delete();
}
ObjectOutputStream oos = null;
try {
file.createNewFile();
oos = new ObjectOutputStream(new FileOutputStream(file));
oos.writeObject(list);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (null != oos) {
try {
oos.close();
} catch (IOException e) {
}
}
}
}
/**
* 生成样本对象，并保存到指定文件
*
* @param sampleSize 样本大小
* @param listSize 样本中List字段长度
* @param mapKeyNum 样本中Map对象Key数量
* @param filePath 样本输出的路径
*/
public static void buildObjectSamples(int sampleSize, int listSize, int mapKeyNum, String filePath) {
List<SampleEntity> list = buildSamples(sampleSize, listSize, mapKeyNum);
File file = new File(filePath);
File parent = file.getParentFile();
if (!parent.exists()) {
parent.mkdirs();
}
if (file.exists()) {
file.delete();
}
ObjectOutputStream oos = null;
try {
file.createNewFile();
oos = new ObjectOutputStream(new FileOutputStream(file));
oos.writeObject(list);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (null != oos) {
try {
oos.close();
} catch (IOException e) {
}
}
}
}
}
来自：http://blog.youkuaiyun.com/accountwcx/article/details/50252657
除了上面个例子，这儿还有一个比较好的：http://blog.51cto.com/chenyanxi/1543445
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