Question

I have the following Spring code, taken from a textbook, that’s returning a NotWritablePropertyException. I’m told I need setters for my Song class, which I thought I’d just done, but it’s apparently not working. I’ve edited my code below. Can anybody help? Here is the code.

package com.springinaction.springidol;

    public class Singer implements Performer {
        private String name = "Someone";
        private Song song;

        public Singer() {
        }

        public Singer(String song) {
            this.song.setTitle(song);
        }

        public Singer(String name, String song) {
            this.song = new Song(song);
            this.name = name;
        }

        public Song getSong() {
            return this.song;
        }

        public void setSong(Song song) {
            this.song = song;
        }

        public void perform() throws PerformanceException {
            System.out.println(name + " IS SINGING " + song.getTitle());
        }
    }

Here is my Song class, which appears to be part of the problem.

public class Song {
    private String title;

    public Song(String song) {
        this.title = song;
    }

    public String getTitle() {
        return this.title;
    }

    public void setTitle(String title) {
        this.title = title;
    }
}

Here are the exceptions.

Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'taylor' defined in class path resource [com/springinaction/springidol/spring-idol.xml]: Initialization of bean failed; nested exception is org.springframework.beans.TypeMismatchException: Failed to convert property value of type [java.lang.String] to required type [com.springinaction.springidol.Song] for property 'song'; nested exception is java.lang.IllegalArgumentException: Cannot convert value of type [java.lang.String] to required type [com.springinaction.springidol.Song] for property 'song': no matching editors or conversion strategy found
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:480)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)
    at java.security.AccessController.doPrivileged(Native Method)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
    at com.springinaction.springidol.SpringIdolMain.main(SpringIdolMain.java:8)
Caused by: org.springframework.beans.TypeMismatchException: Failed to convert property value of type [java.lang.String] to required type [com.springinaction.springidol.Song] for property 'song'; nested exception is java.lang.IllegalArgumentException: Cannot convert value of type [java.lang.String] to required type [com.springinaction.springidol.Song] for property 'song': no matching editors or conversion strategy found
    at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:391)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.convertForProperty(AbstractAutowireCapableBeanFactory.java:1289)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1250)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1010)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:472)
    ... 14 more
Caused by: java.lang.IllegalArgumentException: Cannot convert value of type [java.lang.String] to required type [com.springinaction.springidol.Song] for property 'song': no matching editors or conversion strategy found
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:231)
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:138)
    at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:386)
    ... 18 more

Answer 1

in practice you should have getters and setters for each field unless you are omitting them for a reason.