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Jackson常用方法以及jacksonUtil工具类

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简介:前言:项目中我们通常使用ajax返回json数据格式的形式进行前后端数据交互,所以会用到java数据json数据互相转化,通常我们的做法是在项目中创建一个工具类进行转化处理。如下:我的demo包含了项目中常用的jacksonUti

前言:项目中我们通常使用ajax返回json数据格式的形式进行前后端数据交互,所以会用到java数据json数据互相转化,通常我们的做法是在项目中创建一个工具类进行转化处理。如下:我的demo包含了项目中常用的jacksonUtil类,以及常用的JSON JAVA处理数据转化处理方法。项目结构以及引用jar包如下,jar包中的junit是用于单元测试,与jackson及其相关的包无关。每个部分我都加了注释,直接copy下来运行就可以查看具体效果,下面直接上代码:

Jackson常用方法以及jacksonUtil工具类


实体类book:

package test.entity;

public class Book {

private int bookId;//书的ID

private String author;//作者

private String name;//书名

private int price;//书价

public int getBookId() {

return bookId;

}

public void setBookId(int bookId) {

this.bookId = bookId;

}

public String getAuthor() {

return author;

}

public void setAuthor(String author) {

this.author = author;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getPrice() {

return price;

}

public void setPrice(int price) {

this.price = price;

}

@Override

public String toString() {

return "Book [bookId=" + bookId + ",author=" + author + ",name="

+ name + ",price=" + price + "]";

}

}


jackson以及相关jar包对java以及json数据的具体处理方法,JackSonDemo类。

package test.jackson;

import java.io.IOException;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.HashMap;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

import java.util.Set;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;

import test.entity.Book;

import com.fasterxml.jackson.core.JsonEncoding;

import com.fasterxml.jackson.core.JsonGenerator;

import com.fasterxml.jackson.core.JsonParseException;

import com.fasterxml.jackson.databind.JsonMappingException;

import com.fasterxml.jackson.databind.ObjectMapper;

public class JackSonDemo {

private JsonGenerator jsonGenerator = null;

private ObjectMapper objectMapper = null;

private Book book = null;

/**

* Junit的方法,用于给每个单元测试添加前置条件和结束条件

*/

@Before

public void init() {

// 构建一个Book实例对象并赋值

book = new Book();

book.setAuthor("海明威");

book.setBookId(123);

book.setName("老人与海");

book.setPrice(30);

objectMapper = new ObjectMapper();

try {

jsonGenerator = objectMapper.getJsonFactory().createJsonGenerator(

System.out,JsonEncoding.UTF8);

} catch (IOException e) {

e.printStackTrace();

}

}

@After

public void destory() {

try {

if (jsonGenerator != null) {

jsonGenerator.flush();

}

if (!jsonGenerator.isClosed()) {

jsonGenerator.close();

}

jsonGenerator = null;

objectMapper = null;

book = null;

System.gc();

} catch (IOException e) {

e.printStackTrace();

}

}

/********************** java常见数据类型转JSON ****************************/

/**

* 1.javaBean转化成json---两种方法writeObject/writeValue均可

* jsonGenerator依赖于ObjectMapper创建

*/

@Test

public void javaBeanToJson() {

try {

System.out.println("jsonGenerator");

// 方法一

jsonGenerator.writeObject(book);

System.out.println();

System.out.println("ObjectMapper");

// 方法二

objectMapper.writeValue(System.out,book);

} catch (IOException e) {

e.printStackTrace();

}

}

/**

* List转化成JSON,三种方式

*/

@Test

public void listToJson() {

try {

List<Book> list = new ArrayList<Book>();

Book bookOne = new Book();

bookOne.setAuthor("安徒生");

bookOne.setBookId(456);

bookOne.setName("安徒生童话");

bookOne.setPrice(55);

Book bookTwo = new Book();

bookTwo.setAuthor("安徒生");

bookTwo.setBookId(456);

bookTwo.setName("安徒生童话");

bookTwo.setPrice(55);

list.add(bookOne);

list.add(bookTwo);

// 方式一

System.out.println("方式一jsonGenerator");

jsonGenerator.writeObject(list);

System.out.println();

System.out.println("方式二ObjectMapper");

// 方式二

System.out.println(objectMapper.writeValueAsString(list));

// 方式三

System.out.println("方式三直接通过objectMapper的writeValue方法:");

objectMapper.writeValue(System.out,list);

} catch (IOException e) {

e.printStackTrace();

}

}

/**

* map转化成JSON,两种方式

*/

@Test

public void mapToJSON() {

try {

Map<String,Object> map = new HashMap<String,Object>();

map.put("name",book.getName());

map.put("book",book);

Book newBook = new Book();

newBook.setAuthor("安徒生");

newBook.setBookId(456);

newBook.setName("安徒生童话");

newBook.setPrice(55);

map.put("newBook",newBook);

System.out.println("第一种方式jsonGenerator");

jsonGenerator.writeObject(map);

System.out.println("");

System.out.println("第二种方式objectMapper");

objectMapper.writeValue(System.out,map);

} catch (IOException e) {

e.printStackTrace();

}

}

/*********************** JSON数据类型转java数据 ********************************/

/**

* json'对象'数据转化成javaBean

*/

@Test

public void jsonToJavaBean() {

String json = "{"bookId":"11111","author":"鲁迅","name":"朝花夕拾","price":"45"}";

try {

Book book = objectMapper.readValue(json,Book.class);

System.out.println(book);

} catch (JsonParseException e) {

e.printStackTrace();

} catch (JsonMappingException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

}

/**

* json'数组'数据转化为ArrayList

*/

@Test

public void jsonToArrayList() {

String json = "[{"bookId":"11111","price":"45"},"

+ "{"bookId":"11111","price":"45"}]";

try {

Book[] book = objectMapper.readValue(json,Book[].class);

for (int i = 0; i < book.length; i++) {

// 注意book[i]仅仅是数组,需要通过Arrays.asList()方法转为ArrayList

List<Book> list = Arrays.asList(book[i]);

System.out.println(list);

}

} catch (JsonParseException e) {

e.printStackTrace();

} catch (JsonMappingException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

}

/**

* json转换成map

*/

@Test

public void JsonToMap() {

String json = "{"name":"book","number":"12138","book1":{"bookId":"11111","

+ ""book2":{"bookId":"22222","author":"易中天","name":"祖先","price":"25"}}";

try {

Map<String,Map<String,Object>> maps = objectMapper.readValue(

json,Map.class);

Set<String> key = maps.keySet();

Iterator<String> iter = key.iterator();

while (iter.hasNext()) {

String field = iter.next();

System.out.println(field + ":" + maps.get(field));

}

} catch (JsonParseException e) {

e.printStackTrace();

} catch (JsonMappingException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

}

}


最后,是我们在实际开发项目中使用的jacksonUtil类,应用起来很简单,直接jacksonUtil.bean2Json(Object object)(bean转JSON)或者jacksonUtil.json2Bean(Object object)(JSON转bean)

package test.util;

import java.io.IOException;

import java.io.StringWriter;

import com.fasterxml.jackson.core.JsonFactory;

import com.fasterxml.jackson.core.JsonGenerator;

import com.fasterxml.jackson.core.JsonParseException;

import com.fasterxml.jackson.databind.JsonMappingException;

import com.fasterxml.jackson.databind.ObjectMapper;

/**

* bean转json格式或者json转bean格式,项目中我们通常使用这个工具类进行json---java互相转化

*/

public class JacksonUtil {

private static ObjectMapper mapper = new ObjectMapper();

public static String bean2Json(Object obj) throws IOException {

StringWriter sw = new StringWriter();

JsonGenerator gen = new JsonFactory().createJsonGenerator(sw);

mapper.writeValue(gen,obj);

gen.close();

return sw.toString();

}

public static <T> T json2Bean(String jsonStr,Class<T> objClass)

throws JsonParseException,JsonMappingException,IOException {

return mapper.readValue(jsonStr,objClass);

}

}


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