在
Java 中使用
Jackson 将 JSON 字符串
转换为对象模型，需要借助 `ObjectMapper` 类。`ObjectMapper` 是
Jackson 库的核心类，可用于 JSON 数据和
Java 对象之间的相互
转换[^1][^2][^3]。
以下是使用
Jackson 将 JSON 字符串
转换为对象模型的详细步骤和示例代码：
### 1. 添加依赖
如果使用 Maven，在 `pom.xml` 中添加以下依赖：
```xml
<dependency>
<groupId>com.fasterxml.
jackson.core</groupId>
<artifactId>
jackson-databind</artifactId>
<version>2.15.2</version>
</dependency>
```
如果使用 Gradle，在 `build.gradle` 中添加以下依赖：
```groovy
implementation 'com.fasterxml.
jackson.core:
jackson-databind:2.15.2'
```
### 2. 创建
Java 对象模型
假设要将之前的天气 JSON 字符串
转换为对象，需要创建对应的
Java 类。
```
java
import
java.util.
List;
class WeatherInfo {
private
String city;
private
String date;
private Weather weather;
private
List<Forecast> forecast;
// Getters and Setters
public
String getCity() {
return city;
}
public void setCity(
String city) {
this.city = city;
}
public
String getDate() {
return date;
}
public void setDate(
String date) {
this.date = date;
}
public Weather getWeather() {
return weather;
}
public void setWeather(Weather weather) {
this.weather = weather;
}
public
List<Forecast> getForecast() {
return forecast;
}
public void setForecast(
List<Forecast> forecast) {
this.forecast = forecast;
}
}
class Weather {
private
String condition;
private Temperature temperature;
private int humidity;
private Wind wind;
// Getters and Setters
public
String getCondition() {
return condition;
}
public void setCondition(
String condition) {
this.condition = condition;
}
public Temperature getTemperature() {
return temperature;
}
public void setTemperature(Temperature temperature) {
this.temperature = temperature;
}
public int getHumidity() {
return humidity;
}
public void setHumidity(int humidity) {
this.humidity = humidity;
}
public Wind getWind() {
return wind;
}
public void setWind(Wind wind) {
this.wind = wind;
}
}
class Temperature {
private int min;
private int max;
// Getters and Setters
public int getMin() {
return min;
}
public void setMin(int min) {
this.min = min;
}
public int getMax() {
return max;
}
public void setMax(int max) {
this.max = max;
}
}
class Wind {
private int speed;
private
String direction;
// Getters and Setters
public int getSpeed() {
return speed;
}
public void setSpeed(int speed) {
this.speed = speed;
}
public
String getDirection() {
return direction;
}
public void setDirection(
String direction) {
this.direction = direction;
}
}
class Forecast {
private
String date;
private
String condition;
private Temperature temperature;
// Getters and Setters
public
String getDate() {
return date;
}
public void setDate(
String date) {
this.date = date;
}
public
String getCondition() {
return condition;
}
public void setCondition(
String condition) {
this.condition = condition;
}
public Temperature getTemperature() {
return temperature;
}
public void setTemperature(Temperature temperature) {
this.temperature = temperature;
}
}
```
### 3. 使用 `ObjectMapper` 将 JSON 字符串
转换为对象
```
java
import com.fasterxml.
jackson.databind.ObjectMapper;
public class JsonToObjectExample {
public static void main(
String[] args) {
String json = "{\"city\": \"北京\", \"date\": \"2024-10-15\", \"weather\": {\"condition\": \"晴\", \"temperature\": {\"min\": 10, \"max\": 22}, \"humidity\": 30, \"wind\": {\"speed\": 5, \"direction\": \"北风\"}}, \"forecast\": [{\"date\": \"2024-10-16\", \"condition\": \"多云\", \"temperature\": {\"min\": 11, \"max\": 23}}, {\"date\": \"2024-10-17\", \"condition\": \"小雨\", \"temperature\": {\"min\": 8, \"max\": 18}}]}";
ObjectMapper objectMapper = new ObjectMapper();
try {
WeatherInfo weatherInfo = objectMapper.readValue(json, WeatherInfo.class);
System.out.println("城市: " + weatherInfo.getCity());
System.out.println("日期: " + weatherInfo.getDate());
System.out.println("当天天气状况: " + weatherInfo.getWeather().getCondition());
} catch (Exception e) {
e.printStackTrace();
}
}
}
```
### 代码解释
- 首先，创建 `ObjectMapper` 实例，它是
Jackson 库的核心类，用于处理 JSON 数据和
Java 对象之间的
转换。
- 然后，调用 `readValue` 方法，传入 JSON 字符串和目标
Java 类的 `Class` 对象，将 JSON 字符串
转换为对应的
Java 对象。
- 最后，通过
Java 对象的 getter 方法获取所需的属性值。
本文介绍了一种将JSON字符串转换为List<String>的方法，并通过具体示例展示了如何使用org.codehaus.jackson库实现这一过程。文中包含了异常处理及数据遍历打印的完整流程。
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