Jackson学习四之使用Streaming API创建以及读取JSON参考文章:

Jackson学习四之使用Streaming API创建以及读取JSON

参考文章:

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例子中某些方法已经废弃,直接替换掉了,将原文两个例子放在一个类中:

package com.jingshou.jackson;import java.io.File;import java.io.IOException;import com.fasterxml.jackson.core.JsonEncoding;import com.fasterxml.jackson.core.JsonFactory;import com.fasterxml.jackson.core.JsonGenerator;import com.fasterxml.jackson.core.JsonParser;import com.fasterxml.jackson.core.JsonToken;public class JacksonTest6 {public static void main(String[] args) throws IOException {JsonFactory jfactory = new JsonFactory(); /*** write to file ***/JsonGenerator jGenerator = jfactory.createGenerator(new File("c:\\user.json"), JsonEncoding.UTF8);jGenerator.writeStartObject(); // { jGenerator.writeStringField("name", "mkyong"); // "name" : "mkyong"jGenerator.writeNumberField("age", 29); // "age" : 29 jGenerator.writeFieldName("messages"); // "messages" :jGenerator.writeStartArray(); // [ jGenerator.writeString("msg 1"); // "msg 1"jGenerator.writeString("msg 2"); // "msg 2"jGenerator.writeString("msg 3"); // "msg 3" jGenerator.writeEndArray(); // ] jGenerator.writeEndObject(); // }jGenerator.close();/*** read from file ***/JsonParser jParser = jfactory.createParser(new File("c:\\user.json"));// loop until token equal to "}"while (jParser.nextToken() != JsonToken.END_OBJECT) { String fieldname = jParser.getCurrentName();if ("name".equals(fieldname)) { // current token is "name", // move to next, which is "name"'s value jParser.nextToken(); System.out.println(jParser.getText()); // display mkyong } if ("age".equals(fieldname)) { // current token is "age", // move to next, which is "name"'s value jParser.nextToken(); System.out.println(jParser.getIntValue()); // display 29 } if ("messages".equals(fieldname)) { jParser.nextToken(); // current token is "[", move next // messages is array, loop until token equal to "]" while (jParser.nextToken() != JsonToken.END_ARRAY) { // display msg1, msg2, msg3 System.out.println(jParser.getText()); } } } jParser.close();}}

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小结:

对于性能要求高的程序,推荐使用流API,否则使用其他方法不管是创建JsonGenerator还是JsonParser,都是使用JsonFactory

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