抽象的阶梯

# 第03章 GSON

# 1.1 添加依赖

// https://mvnrepository.com/artifact/com.google.code.gson/gson
compile group: 'com.google.code.gson', name: 'gson', version: '2.8.4'
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<!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->
<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.8.4</version>
</dependency>
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# 1.2 对象转换为json

package com.changan.org_json;

import com.google.gson.Gson;

public class GSONCreateSample {
    public static void main(String[] args) {
        Person wangxiaoer = new Person();
        wangxiaoer.setName("王小二");
        wangxiaoer.setAge(25.2);
        wangxiaoer.setBirthday("1990-08-23");
        wangxiaoer.setSchool("蓝翔");
        wangxiaoer.setMajor(new String[]{"理发", "挖掘机"});
        wangxiaoer.setHas_girfriend(false);
        wangxiaoer.setCar(null);
        wangxiaoer.setHouse(null);
        wangxiaoer.setComment("这是一个注释");
        Gson gson = new Gson();
        System.out.println(gson.toJson(wangxiaoer));
    }
}
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# 1.3 自定义json中显示的名称@SerializedName

package com.changan.org_json;

import com.google.gson.annotations.SerializedName;

public class Person {
    @SerializedName("person_name")
    private String name;
    @SerializedName("person_school")
    private String school;
    private boolean has_girfriend;
    private double age;
    private Object car;
    private Object house;
    private String[] major;
    private String comment;
    private String birthday;

    // getter & setter
}
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# 1.4 GsonBuilder个性化定制

# 1.4.1 setPrettyPrinting json美化

import com.google.gson.GsonBuilder;

public class GSONCreateSample {
    public static void main(String[] args) {
        Person wangxiaoer = new Person();
        wangxiaoer.setName("王小二");
        wangxiaoer.setAge(25.2);
        wangxiaoer.setBirthday("1990-08-23");
        wangxiaoer.setSchool("蓝翔");
        wangxiaoer.setMajor(new String[]{"理发", "挖掘机"});
        wangxiaoer.setHas_girfriend(false);
        wangxiaoer.setCar(null);
        wangxiaoer.setHouse(null);
        wangxiaoer.setComment("这是一个注释");
        GsonBuilder builder = new GsonBuilder();
        builder.setPrettyPrinting();
        Gson gson = builder.create();
        System.out.println(gson.toJson(wangxiaoer));
    }
}
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# 1.4.2 setFieldNamingStrategy 修改属性名称

使用FieldNamingStrategy()回调函数：个性化定制，灵活定制JSON

package com.changan.org_json;

import com.google.gson.FieldNamingStrategy;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import java.lang.reflect.Field;

public class GSONCreateSample {
    public static void main(String[] args) {
        Person wangxiaoer = new Person();
        wangxiaoer.setName("王小二");
        wangxiaoer.setAge(25.2);
        wangxiaoer.setBirthday("1990-08-23");
        wangxiaoer.setSchool("蓝翔");
        wangxiaoer.setMajor(new String[]{"理发", "挖掘机"});
        wangxiaoer.setHas_girfriend(false);
        wangxiaoer.setCar(null);
        wangxiaoer.setHouse(null);
        wangxiaoer.setComment("这是一个注释");
        GsonBuilder builder = new GsonBuilder();
        builder.setPrettyPrinting();
        builder.setFieldNamingStrategy(new FieldNamingStrategy() {
            @Override
            public String translateName(Field f) {
                if (f.getName().equals("age")) {
                    return "person_age";
                }
                return f.getName();
            }
        });
        Gson gson = builder.create();
        System.out.println(gson.toJson(wangxiaoer));
    }
}
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# 1.5 使用transient忽略某些属性

在Person中定义transient修饰的属性：

private transient String ignore;

public String getIgnore() {
    return ignore;
}

public void setIgnore(String ignore) {
    this.ignore = ignore;
}
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# 1.6 Gson解析

# 1.6.1 解析JSON文件

GSON解析JSON文件：可以直接生成对象（基于反射机制），约定优于配置

package com.changan.org_json;

import com.google.gson.Gson;
import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;

public class GsonReadSample {
    public static void main(String[] args) throws IOException {
        File file = new File(ReadJsonSample.class.getResource("/wangxiaoer.json").getFile());
        String content = FileUtils.readFileToString(file, "UTF-8");
        Gson gson = new Gson();
        Person person = gson.fromJson(content, Person.class);
        System.out.println(person);
    }
}
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# 1.6.2 解析带日期转换

创建新的PersonWithDate

package com.changan.org_json;

import java.util.Arrays;
import java.util.Date;

public class PersonWithDate {
    //@SerializedName("person_name")
    private String name;
    //@SerializedName("person_school")
    private String school;
    private boolean has_girfriend;
    private double age;
    private Object car;
    private Object house;
    private String[] major;
    private String comment;
    private Date birthday;

    // getter & setter & toString
}
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使用GsonBuilder的setDateFormat方法

package com.changan.org_json;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;

public class GsonReadSample {
    public static void main(String[] args) throws IOException {
        File file = new File(ReadJsonSample.class.getResource("/wangxiaoer.json").getFile());
        String content = FileUtils.readFileToString(file, "UTF-8");
        GsonBuilder gsonBuilder = new GsonBuilder();
        Gson gson = gsonBuilder.setDateFormat("yyyy-MM-dd").create();
        PersonWithDate person = gson.fromJson(content, PersonWithDate.class);
        System.out.println(person.getBirthday().toLocaleString());
    }
}
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# 1.6.3 集合类解析

修改PersonWitDate

package com.changan.org_json;

import java.util.Date;
import java.util.List;

public class PersonWithDate {
    //@SerializedName("person_name")
    private String name;
    //@SerializedName("person_school")
    private String school;
    private boolean has_girfriend;
    private double age;
    private Object car;
    private Object house;
    //替换为集合类
    private List<String> major;
    private String comment;
    private Date birthday;
	// getter & setter & toString
}
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package com.changan.org_json;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;

public class GsonReadSample {
    public static void main(String[] args) throws IOException {
        File file = new File(ReadJsonSample.class.getResource("/wangxiaoer.json").getFile());
        String content = FileUtils.readFileToString(file, "UTF-8");
        GsonBuilder gsonBuilder = new GsonBuilder();
        Gson gson = gsonBuilder.setDateFormat("yyyy-MM-dd").create();
        PersonWithDate person = gson.fromJson(content, PersonWithDate.class);
        System.out.println(person.getBirthday().toLocaleString());

        System.out.println(person.getMajor());
        System.out.println(person.getMajor().getClass());
    }
}
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Last Updated: 10/20/2019, 11:49:45 PM

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