How to deal with super-large objects and super-large JSON text with fastjson
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Take a look at the sample code:
Example object:
Package json.fastjson.StreamApi;import java.util.HashMap;import java.util.Map;public class VO {private int id;private Map attributes= new HashMap (); public VO (int id) {super (); this.id = id;} public int getId () {return id;} public void setId (int id) {this.id = id;} public Map getAttributes () {return attributes;} @ Overridepublic String toString () {return "VO [id=" + id + ", attributes=" + attributes + "]" 1. Serialization
1.1.The serialization of super large JSON array
If your JSON format is a huge JSON array with many elements, call startArray first, then write objects one by one, and then call endArray.
Test class:
Package json.fastjson.StreamApi;import java.io.FileWriter;import java.io.IOException;import com.alibaba.fastjson.JSONWriter;public class TestHugeArraySerialize {public static void main (String [] args) throws IOException {JSONWriter writer = new JSONWriter (new FileWriter ("hugeArray.json")); writer.startArray (); for (int I = 0; I
< 10; ++i) { writer.writeValue(new VO(i)); } writer.endArray(); writer.close(); }} 输出结果： 程序运行之后会产生一个文件： 文件内容： [{"attributes":{},"id":0},{"attributes":{},"id":1},{"attributes":{},"id":2},{"attributes":{},"id":3},{"attributes":{},"id":4},{"attributes":{},"id":5},{"attributes":{},"id":6},{"attributes":{},"id":7},{"attributes":{},"id":8},{"attributes":{},"id":9}] 1 1.2、超大JSON对象序列化 如果你的JSON格式是一个巨大的JSONObject，有很多Key/Value对，则先调用startObject，然后挨个写入Key和Value，然后调用endObject。 测试类： package json.fastjson.StreamApi;import java.io.FileWriter;import java.io.IOException;import com.alibaba.fastjson.JSONWriter;public class TestHugeObjectSerialize {public static void main(String[] args) throws IOException { JSONWriter writer = new JSONWriter(new FileWriter("hugeObject.json")); writer.startObject();for (int i = 0; i < 10; ++i) { writer.writeKey("x" + i); writer.writeValue(new VO(i)); } writer.endObject(); writer.close(); }} 输出结果： 程序运行之后会产生一个文件：Contents of the file:
{"x0": {"attributes": {}, "id": 0}, "x1": {"attributes": {}, "id": 1}, "x2": {"attributes": {}, "id": 2}, "x3": {"attributes": {}, "id": 3}, "x4": {"attributes": {}, "id": 4}, "x5": {"attributes": {}, "id": 5}, "x6": {"attributes": {} "id": 6}, "x7": {"attributes": {}, "id": 7}, "x8": {"attributes": {}, "id": 8}, "x9": {"attributes": {}, "id": 9}}
one
2. Deserialization
2.1.The deserialization of super large JSON array
Test class:
Package json.fastjson.StreamApi;import java.io.FileReader;import java.io.IOException;import com.alibaba.fastjson.JSONReader;public class TestHugeArrayDeserialize {public static void main (String [] args) throws IOException {/ / read the output file above JSONReader reader = new JSONReader (new FileReader ("hugeArray.json")); reader.startArray (); while (reader.hasNext ()) {VO vo = reader.readObject (VO.class); System.out.println (vo) } reader.endArray (); reader.close ();}}
Output result:
VO [id=0, attributes= {}] VO [id=1, attributes= {}] VO [id=2, attributes= {}] VO [id=3, attributes= {}] VO [id=4, attributes= {}] VO [id=5, attributes= {}] VO [id=6, attributes= {}] VO [id=7, attributes= {}] VO [id=8, attributes= {}] VO [id=9, attributes= {}]
2.2.The deserialization of very large JSON objects
Test class:
Package json.fastjson.StreamApi;import java.io.FileReader;import java.io.IOException;import com.alibaba.fastjson.JSONReader;public class TestHugeObjectDeserialize {public static void main (String [] args) throws IOException {/ / read the output file above JSONReader reader = new JSONReader (new FileReader ("hugeObject.json")); reader.startObject (); while (reader.hasNext ()) {String key = reader.readString (); VO vo = reader.readObject (VO.class) System.out.println (key + ":" + vo);} reader.endObject (); reader.close ();}}
Output result:
X0:VO [id=0, attributes= {}] x1:VO [id=1, attributes= {}] x2:VO [id=2, attributes= {}] x3:VO [id=3, attributes= {}] x4:VO [id=4, attributes= {}] x5:VO [id=5, attributes= {}] x6:VO [id=6, attributes= {}] x7:VO [id=7, attributes= {}] x8:VO [id=8, attributes= {}] x9:VO [id=9, attributes= {}] Thank you for your reading The above is the content of "how to use fastjson to deal with super-large objects and super-large JSON text". After the study of this article, I believe you have a deeper understanding of how to use fastjson to deal with super-large objects and super-large JSON text. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!
